Redo how daterangepicker is open/closed, fixing a couple problems.

- Allows clicking the trigger button/element to hide the picker (like regular bootstrap dropdowns)
- When a Bootstrap dropdown is open, clicking the daterangepicker element should close/hide the Bootstrap dropdown
- When a daterangepicker is open, clicking a Bootstrap dropdown element should close/hide the daterangepicker.
Merge pull request #270 from elasticsales/dropdowninteraction

Plays nicely with Bootstrap dropdowns