Merge pull request #1 from bentoner/master

Give credit to Bill.
Front page shows papers from all categories
Upgrade to Rails 3.2.13, fix routing regression
Add sign up link on header
Add MathJax for comments
Add bootstrap-y pagedown editor
(markdown isn't rendered in actual comments yet)
Comments now correctly support latex and markdown
Throw a 404 on non-existent feed instead of index
Comment editor is looking closer to final state
Fix display of papers when user is logged out
Minor comment tweaks
Use https to access mathjax cdn
Fix comment usability issues
Change latex link to tooltip
Handle case of empty feeds
Apply mathjax to abstracts
Latex-ify paper titles too
Fix SSL certificate issues with MathJax
Don't show mathjax errors/undefined latex in red
Remove mathjax context menu