Cleanup stylesheets formatting and delete unused files

As I try to update the UI I went through all the CSS files and gave them consistent formatting. Too many extra blank lines and other formatting errors. Also deleted 2 files which were not being used at all.
Formatting for signup and create challenge pages
FIX BUG - challenge path now working for interactive challenges

Before if you created an interactive challenge and tried to navigate to it you'd get a method error. Added a new method in helpers to return the proper route based on whether a challenge is interactive or not.
Add formatting for interactive page and challenges rows

Made the rows a new size to handle larger pictures. Also made pictures from 20x20 to 28x28.
Merge branch 'design'