Add support for tabindex on focusser input

This change adds the ability to specify tabindex on the ui-select
element and have it passed to the focusser input.  The tabindex is
removed from the ui-select div after it is applied to the focusser
input.
Add support for tabindex on searchInput

If the ui-select is in multiple mode, add the tabindex to the
search input instead of the focusser.
Merge pull request #181 from corystevens/feat-tabindex-on-focusser

Add support for tabindex on focusser input