Polymer 1.0.0

• Updated for the release of Polymer 1.0.0
• Documentation now is fully viewable on the component page

Initial release

Basic functionality additions to iron-selector:

• Ability to require selection.
• Reset items.
• Validates any values set to selected or selectedValues, removing invalid values.
• plastik-selector can be switched between multi-selection mode on the fly and will retain its selection, switching between selected and selectedValues as necessary. Added unit test which tests this functionality.