diff --git a/CONTRIBUTING.rst b/CONTRIBUTING.rst
index 01143337..3ffea063 100644
--- a/CONTRIBUTING.rst
+++ b/CONTRIBUTING.rst
@@ -1,12 +1,13 @@
+######################
 Contributing to HTTPie
 ######################
 
-Bug reports and code and documentation patches are greatly appreciated. You can
-also help by using the development version of HTTPie and reporting any bugs you
-might encounter.
+Bug reports and code and documentation patches are welcome. You can
+help this project also by using the development version of HTTPie
+and by reporting any bugs you might encounter.
 
-Bug Reports
-===========
+1. Reporting bugs
+=================
 
 **It's important that you provide the full command argument list
 as well as the output of the failing command.**
@@ -15,12 +16,12 @@ to your bug report, e.g.:
 
 .. code-block:: bash
 
-    $ http --debug [arguments that trigger the error]
-    [complete output]
+    $ http --debug [COMPLETE ARGUMENT LIST THAT TRIGGERS THE ERROR]
+    [COMPLETE OUTPUT]
 
 
-Contributing Code and Documentation
-===================================
+2. Contributing Code and Docs
+=============================
 
 Before working on a new feature or a bug, please browse `existing issues`_
 to see whether it has been previously discussed. If the change in question
@@ -28,8 +29,11 @@ is a bigger one, it's always good to discuss before your starting working on
 it.
 
 
-Development Environment
------------------------
+Creating Development Environment
+--------------------------------
+
+Go to https://github.com/jkbrzt/httpie and fork the project repository.
+
 
 .. code-block:: bash
 
@@ -52,44 +56,56 @@ Making Changes
 Please make sure your changes conform to `Style Guide for Python Code`_ (PEP8).
 
 
-Tests
------
+Testing
+-------
 
 Before opening a pull requests, please make sure the `test suite`_ passes
-in all of the `supported Python environments`_. You should also **add tests
-for any new features and bug fixes**.
+in all of the `supported Python environments`_. You should also add tests
+for any new features and bug fixes.
 
-HTTPie uses `pytest`_ and `Tox`_.
+HTTPie uses `pytest`_ and `Tox`_ for testing.
+
+
+Running all tests:
+******************
 
 .. code-block:: bash
 
-    ### Running all tests:
-
-    # Current Python
+    # Run all tests on the current Python interpreter
     make test
 
-    # Current Python with coverage
+    # Run all tests on the current Python with coverage
     make test-cover
 
-    # All the supported and available Pythons via Tox
+    # Run all tests in all of the supported and available Pythons via Tox
     make test-tox
 
-    ### Running specific tests:
 
-    # Current Python
-    pytest tests/test_uploads.py
+Running specific tests:
+***********************
 
-    # All Pythons
+.. code-block:: bash
+
+    # Run specific tests on the current Python
+    py.test tests/test_uploads.py
+    py.test tests/test_uploads.py::TestMultipartFormDataFileUpload
+    py.test tests/test_uploads.py::TestMultipartFormDataFileUpload::test_upload_ok
+
+    # Run specific tests on the on all Pythons via Tox
     tox -- tests/test_uploads.py --verbose
+    tox -- tests/test_uploads.py::TestMultipartFormDataFileUpload --verbose
+    tox -- tests/test_uploads.py::TestMultipartFormDataFileUpload::test_upload_ok --verbose
 
 
-Don't forget to add yourself to `AUTHORS.rst`_.
+-----
+
+Don't forget to add yourself to `AUTHORS`_!
 
 
 .. _Tox: http://tox.testrun.org
 .. _supported Python environments: https://github.com/jkbrzt/httpie/blob/master/tox.ini
 .. _existing issues: https://github.com/jkbrzt/httpie/issues?state=open
-.. _AUTHORS.rst: https://github.com/jkbrzt/httpie/blob/master/AUTHORS.rst
+.. _AUTHORS: https://github.com/jkbrzt/httpie/blob/master/AUTHORS.rst
 .. _pytest: http://pytest.org/
 .. _Style Guide for Python Code: http://python.org/dev/peps/pep-0008/
 .. _test suite: https://github.com/jkbrzt/httpie/tree/master/tests
diff --git a/Makefile b/Makefile
index 26b65083..54f1ede6 100644
--- a/Makefile
+++ b/Makefile
@@ -1,3 +1,7 @@
+#
+# See ./CONTRIBUTING.rst
+#
+
 VERSION=$(shell grep __version__ httpie/__init__.py)
 REQUIREMENTS="requirements-dev.txt"
 TAG="\n\n\033[0;32m\#\#\# "
@@ -7,6 +11,8 @@ all: test
 
 uninstall-httpie:
 	@echo $(TAG)Removing existing installation of HTTPie$(END)
+	@echo "(NOTE: uninstall httpie manually if this fails)"
+	@echo
 	- pip uninstall --yes httpie >/dev/null
 	! which http
 	@echo
@@ -22,7 +28,7 @@ init: uninstall-httpie
 	@echo
 
 test: init
-	@echo $(TAG)Running tests in on current Python with coverage $(END)
+	@echo $(TAG)Running tests on the current Python interpreter with coverage $(END)
 	py.test --cov ./httpie --cov ./tests --doctest-modules --verbose ./httpie ./tests
 	@echo
 
diff --git a/httpie/config.py b/httpie/config.py
index 9f28da17..64f72b2b 100644
--- a/httpie/config.py
+++ b/httpie/config.py
@@ -6,11 +6,11 @@ from httpie import __version__
 from httpie.compat import is_windows
 
 
-DEFAULT_CONFIG_DIR = os.environ.get(
+DEFAULT_CONFIG_DIR = str(os.environ.get(
     'HTTPIE_CONFIG_DIR',
     os.path.expanduser('~/.httpie') if not is_windows else
     os.path.expandvars(r'%APPDATA%\\httpie')
-)
+))
 
 
 class BaseConfigDict(dict):
diff --git a/tests/utils.py b/tests/utils.py
index aad27395..5efdd011 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -53,7 +53,7 @@ class TestEnvironment(Environment):
     stdout_isatty = True
     is_windows = False
 
-    _shutil = shutil  # needed by __del__ (would get gc'd)
+    _shutil_rmtree = shutil.rmtree  # needed by __del__ (would get gc'd)
 
     def __init__(self, **kwargs):
 
@@ -72,7 +72,7 @@ class TestEnvironment(Environment):
 
     def __del__(self):
         if self.delete_config_dir:
-            self._shutil.rmtree(self.config_dir)
+            self._shutil_rmtree(self.config_dir)
 
 
 def http(*args, **kwargs):
diff --git a/tox.ini b/tox.ini
index 6cab5b95..f746660f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,18 +1,22 @@
 # Tox (http://tox.testrun.org/) is a tool for running tests
-# in multiple virtualenvs.
-# Run:
-# $ pip install -r requirements-dev.txt
-# $ tox
+# in multiple virtualenvs. See ./CONTRIBUTING.rst
 
 
 [tox]
-envlist = py26, py27, py34, pypy
+envlist = py26, py27, py35, pypy
 
 
 [testenv]
 deps =
+    mock
     pytest
     pytest-httpbin>=0.0.6
 
+
 commands =
-    py.test --verbose --doctest-modules --basetemp={envtmpdir} {posargs:./tests ./httpie}
+    # NOTE: the order of the directories in posargs seems to matter.
+    # When changed, then many ImportMismatchError exceptions occurrs.
+    py.test \
+        --verbose \
+        --doctest-modules \
+        {posargs:./httpie ./tests}