Add Closure compiler externs and a concrete EventType enum for paper-radio-button. Note that the externs are dependent on the Polymer externs in the pull request at https://github.com/Polymer/polymer/pull/769.
Add a license to the externs
Add ignores to bower.json for the externs and event type files.
Move externs and eventtype to an externs directory. Update bower.json.
Merge pull request #8 from jklein24/master

Add Closure compiler externs and a concrete EventType enum.