Caching the minimakect input field for performance

Caching the minimakect input field for performance and to save some
bytes.
Added option to remove empty option tag

Was removed by default, now optional. This enables the user to revert
back to an "empty" state.
Increased element caching

Some more element caching and jquery performance optimizations while
keeping it mini.
Merged with latest upstream
Merge pull request #25 from Frique/master

Increased element caching & added option to keep empty option tag.