Instructions, Fixes, and Performance Enhancements

• Updated README to give users instructions for configuration.
• Added "Credits" at the bottom for attribution.
• Added the MIT License.
• Moved jQuery UI import to afterRender method for performance improvement when running more than one instance of widget, and switched to cached ajax call.

v2: Merge pull request #2 from adamdehaven/improvements

A nice code overhaul by @adamdehaven