Issue 367: Clear on tab out
When tabbing out on multi select, the dropdown will be closed. This ensures the
search text to be cleared out.
onDropdownOpened callback implementation
Also allow to pass undefined to the setActiveItem method, so the popup won't show any active item when opened.
Merge branch 'fix-invalidtextontabout'

Conflicts:
	dist/select.css
	dist/select.js
	dist/select.min.css
	dist/select.min.js
	examples/demo-multi-select.html
	test/select.spec.js
New build after merge