pep8 clean up
Bring code into line with PEP8 coding conventions for python.

A summary of some things changed and the relevant part of PEP8 showing
why I changed it.

-Constants should be upper case with underscores. In word_freq.py
 punctuation and excludedWords are constants so they are changed to
 PUNCTUATION and EXCLUDED_WORDS.
 http://www.python.org/dev/peps/pep-0008/#constants

-Function names should be lower case with underscores. In word_freq.py
 the parseText, processRedditor, processSubmission, and processSubreddit
 functions are changed to parse_text, process_redditor,
 process_submission, and process_subreddit. in tests/test-functions.py
 the names of the methods of the TestSequenceFunctions class have been
 changed for the same reasons.
 http://www.python.org/dev/peps/pep-0008/#function-names

-Variable names should be lower case with underscores.
 http://www.python.org/dev/peps/pep-0008/#global-variable-names

-Top level functions and classes should be separate by two blank lines.
 Added a blank line above TestSequenceFunctions to separate in two lines
 from the imports.
 http://www.python.org/dev/peps/pep-0008/#blank-lines

-Removed extraneous witespace from popular_words dict in
 tests/test-functions.py. I also separated each key value pair onto it's
 own line so that the line was no longer more than 80 chars long.

I'm not trying to be picky with this commit. I see from the commit logs
that you've tried to bring things into line with PEP8 before. I just
thought I'd give you a hand.