Update angular.js to 1.2.15

Pulled packages from http://code.angularjs.org/
Copied the pattern of previous updates to angular.js:
- unzipped version zip file from official source above
- rm \*.map errors.json version.\*
- rm -rf i18n docs
- chmod 755 *

Updated package.json to point to 1.2.15 (This is the latest stable, but also included the beta directories.)