Added file upload support

It is now possible to send multipart/form-data requests.

Note that the --file option used previously has been removed
because it didn't allow you specify the field name.

Example:

    http -f POST example.com field-name@/path/to/file

tests/file.txt

@@ -0,0 +1 @@
+__test_file_content__

tests/tests.py

@@ -0,0 +1,135 @@
+# coding:utf8
+import os
+import sys
+import unittest
+import argparse
+from StringIO import StringIO
+
+
+TESTS_ROOT = os.path.dirname(__file__)
+sys.path.insert(0, os.path.abspath(os.path.join(TESTS_ROOT, '..')))
+from httpie import __main__
+from httpie import cli
+
+
+TERMINAL_COLOR_CHECK = '\x1b['
+
+
+def http(*args, **kwargs):
+    http_kwargs = {
+        'stdin_isatty': True,
+        'stdout_isatty': False
+    }
+    http_kwargs.update(kwargs)
+    stdout = http_kwargs.setdefault('stdout', StringIO())
+    __main__.main(args=args, **http_kwargs)
+    return stdout.getvalue()
+
+
+class BaseTest(unittest.TestCase):
+
+    if sys.version < (2, 7):
+        def assertIn(self, member, container, msg=None):
+            self.assert_(member in container, msg)
+
+        def assertNotIn(self, member, container, msg=None):
+            self.assert_(member not in container, msg)
+
+        def assertDictEqual(self, d1, d2, msg=None):
+            self.assertEqual(set(d1.keys()), set(d2.keys()), msg)
+            self.assertEqual(sorted(d1.values()), sorted(d2.values()), msg)
+
+
+class TestItemParsing(BaseTest):
+
+    def setUp(self):
+        self.kv = cli.KeyValueType(
+            cli.SEP_HEADERS,
+            cli.SEP_DATA,
+            cli.SEP_DATA_RAW_JSON
+        )
+
+    def test_invalid_items(self):
+        items = ['no-separator']
+        for item in items:
+            self.assertRaises(argparse.ArgumentTypeError,
+                              lambda: self.kv(item))
+
+    def test_valid_items(self):
+        headers, data = cli.parse_items([
+            self.kv('string=value'),
+            self.kv('header:value'),
+            self.kv('list:=["a", 1, {}, false]'),
+            self.kv('obj:={"a": "b"}'),
+            self.kv('eh:'),
+            self.kv('ed='),
+            self.kv('bool:=true'),
+        ])
+        self.assertDictEqual(headers, {
+            'header': 'value',
+            'eh': ''
+        })
+        self.assertDictEqual(data, {
+            "ed": "",
+            "string": "value",
+            "bool": True,
+            "list": ["a", 1, {}, False],
+            "obj": {"a": "b"}
+        })
+
+
+class TestHTTPie(BaseTest):
+
+    def test_get(self):
+        http('GET', 'http://httpbin.org/get')
+
+    def test_json(self):
+        response = http('POST', 'http://httpbin.org/post', 'foo=bar')
+        self.assertIn('"foo": "bar"', response)
+
+    def test_form(self):
+        response = http('--form', 'POST', 'http://httpbin.org/post', 'foo=bar')
+        self.assertIn('"foo": "bar"', response)
+
+    def test_headers(self):
+        response = http('GET', 'http://httpbin.org/headers', 'Foo:bar')
+        self.assertIn('"User-Agent": "HTTPie', response)
+        self.assertIn('"Foo": "bar"', response)
+
+
+class TestPrettyFlag(BaseTest):
+    """Test the --pretty / --ugly flag handling."""
+
+    def test_pretty_enabled_by_default(self):
+        r = http('GET', 'http://httpbin.org/get', stdout_isatty=True)
+        self.assertIn(TERMINAL_COLOR_CHECK, r)
+
+    def test_pretty_enabled_by_default_unless_stdin_redirected(self):
+        r = http('GET', 'http://httpbin.org/get', stdout_isatty=False)
+        self.assertNotIn(TERMINAL_COLOR_CHECK, r)
+
+    def test_force_pretty(self):
+        r = http('--pretty', 'GET', 'http://httpbin.org/get', stdout_isatty=False)
+        self.assertIn(TERMINAL_COLOR_CHECK, r)
+
+    def test_force_ugly(self):
+        r = http('--ugly', 'GET', 'http://httpbin.org/get', stdout_isatty=True)
+        self.assertNotIn(TERMINAL_COLOR_CHECK, r)
+
+
+class TestFileUpload(BaseTest):
+
+    def test_non_existent_file_raises_parse_error(self):
+        self.assertRaises(cli.ParseError, http,
+            '--form', '--traceback',
+            'POST', 'http://httpbin.org/post',
+            'foo@/__does_not_exist__')
+
+    def test_upload_ok(self):
+        r = http('--form', 'POST', 'http://httpbin.org/post',
+             'test-file@%s' % os.path.join(TESTS_ROOT, 'file.txt'))
+        self.assertIn('"test-file": "__test_file_content__', r)
+
+
+if __name__ == '__main__':
+    unittest.main()