Package.json: Add license field

Author: joallard

package.json

@@ -14,6 +14,7 @@
   "description": "Selectize is a jQuery-based custom <select> UI control. Useful for tagging, contact lists, country selectors, etc.",
   "version": "0.12.1",
   "author": "Brian Reavis <brian@thirdroute.com>",
+  "license": "Apache-2.0",
   "repository": {
     "type": "git",
     "url": "git://github.com/brianreavis/selectize.js.git"