Added proxy support with http_proxy configuration

Sites sections of praw.ini now handle the optional directive
'http_proxy'.
Example
[reddit.com]
http_proxy:127.0.0.1:8000

Available URI are the ones handled by the Requests python module.
Proxy authentication would work with:
http_proxy:user:password@host:port

All tests passing (regular tests as well as python setup.py test -s
praw.tests.OAuth2Test
Style changes and version bump.
Change to pytest from unittest
Split big test file into files with 1 test class.
Re-add init file to avoid test package error.
Fix comparison bug in test.

Ungilded comments have value 0 for gilded. Gilded have > 0
Simplify loops in test with first and all
Flatten and remove usage of unittest
Move getting normal testing subreddit into helper
Fix bug in image_test

The final assert creates a list of booleans. They intended to
test whether a file had been uploaded, but didn't since.
assert [False, False, False] doesn't raise an error.
Pylint fixes
Allow test functions to have longer names.
Make tests skippable where appropriate

This was impossible before because skips were first
introduced to unittest in python version 2.7 and
PRAW is designed to work with python 2.6+.
(SQUASH) A few more lint fixes
Merge comment_*_test files into comment_test
Final cleanup of test PR

Removed all instances of six.next. PRAW works for python 2.6+
and the builtin function next was introduced in python 2.6, so
we can just use the builtin.

Removed docstring in praw/tests/helper. It was the left-over
docstring from the original big test file. There is currently
no module docstrings for any of the testing files. Their title
should be sufficient.

Fix misspellings of logged in 3 functions in access_control_test