Updates timeline to begin at 1940 when appropriate
JSHint fixes
Adds ajax loader + removes timeline if no entries

Commit was a bit big so I'll list what I did:

- Added animate.min.css from https://github.com/daneden/animate.css
- Added ajax-loader.gif image from http://www.ajaxload.info/
- Used the ajax spinner to incorporate a loading state
- Used animate.css to add animations to showing/hiding the timeline and it's ajax spinner
- Moved all JS from timeline.html to the end of timeline.js