chore(release): calculate the cdnVersion on every build

The CDN version of angular is now calculated on every build,
by looking at the tags in angular/angular.js, sorting them
by semver and checking against ajax.googleapis.com which
one is available.

package.json

@@ -1,7 +1,6 @@
 {
   "name": "angularjs",
   "branchVersion": "1.3.*",
-  "cdnVersion": "1.3.0-beta.3",
   "repository": {
     "type": "git",
     "url": "https://github.com/angular/angular.js.git"