Page loading optimizations.

Enabled gzip compression on server.
Included min files of bootstrap and query.
Moved header javascript to separate file for caching.
Home page now uses main header include.
Replaced lorem ipsum text on front page with introduction text.
Copy change
User admin screen now displays properly.

Before if was all fields mashed together. Now using the Django admin template.
Course instructors are now displayed properly on course listings.
Added a course published field so courses can be constructed before being published.
Course page no longer shows categories that have no courses associated with them.

Resolves #39 and #42