Add tox.ini for tox (http://tox.testrun.org/)

.gitignore

@@ -2,3 +2,4 @@ dist
 httpie.egg-info
 build
 *.pyc
+.tox

tox.ini

@@ -0,0 +1,19 @@
+# Tox (http://tox.testrun.org/) is a tool for running tests
+# in multiple virtualenvs. This configuration file will run the
+# test suite on all supported python versions. To use it, "pip install tox"
+# and then run "tox" from this directory.
+
+[tox]
+envlist = py26, py27, py30, py31, py32, pypy
+
+[testenv]
+commands = {envpython} setup.py test
+
+[testenv:py26]
+deps = argparse
+
+[testenv:py30]
+deps = argparse
+
+[testenv:py31]
+deps = argparse