Use selectedIndex instead of value for tracking change events.

Fixes #1024 and #962
Merge branch 'master' into use-selectedIndex-for-change

Conflicts:
	chosen/chosen.jquery.min.js
	chosen/chosen.proto.min.js
Merge branch 'master' into use-selectedIndex-for-change

Conflicts:
	chosen/chosen.jquery.min.js
	chosen/chosen.proto.js
	chosen/chosen.proto.min.js
Merge pull request #1147 from harvesthq/use-selectedIndex-for-change

Use selectedIndex instead of value for tracking change events.