Fix white background for comments.

Add a content_script to
http://apis.google.com/u/0/wm/4/_/widget/render/comments*.
Fix comment injection script not being loaded when logged out.
Style sheet fixes for comments.
More style sheet fixes for comments.

Make upvote/downvote arrows display correct colors when hovering.
Fix the background of special commenter names not being darkened.
Style the score of each comment.
Fix white color on the homepage when not signed in.
Fix extension enable/disable toggle.

Fix a regression introduced in 31d8d2ce17c7909b10610f8415a5a40597b5e61e.
Merge pull request #6 from NSDex/master

Fix white color on comments, fix white color on the homepage when signed out.