Make setters and public method chainable.

Signed-off-by: tomalec <tomalecpub@gmail.com>
Tests for chainable methods
Merge branch 'chainableMethods' of git://github.com/tomalec/bootstrap-datepicker into tomalec-chainableMethods

Conflicts:
	js/bootstrap-datepicker.js
Merge pull request #722 from tomalec/chainableMethods