Bump NPM version to 0.5.0 in preparation for publishing.

The minor version bump is due to the switch from esprima (harmony) to
esprima-fb. I don't anticipate any backwards compatibility problems, but
this change is potentially user-visible, so it needs to be optional.

package.json

@@ -16,7 +16,7 @@
     "desugaring",
     "ES6"
   ],
-  "version": "0.4.12",
+  "version": "0.5.0",
   "homepage": "http://github.com/facebook/regenerator",
   "repository": {
     "type": "git",