Fix GetThingByFullname() and Post.Comment()

Fixes GetThingByFullname() only working on comments, not posts
Fixes Post.Comment() returning a basically empty object
Adds tests to prove both of the above function correctly
Merge pull request #120 from YMIndustries/fullnamefixes

Fix GetThingByFullname() and Post.Comment()
Test Commit
Pedantic little change, but checking the count of the passbits stack is more than 0 prevents program from crashing if you press backspace too many times.
Merge pull request #122 from adzjwarner/master

Sorry, I might be using you to experiment with github! ;)
Add ability to search subreddits
Fix issue in search
Merge branch 'master' of https://github.com/SirCmpwn/RedditSharp