Clear local storage data upon new version of AS

#### To test:
 - npm install
 - grunt build
 - Run your web app with recently compiled version of AS and make sure that local storage has new  AS_version key that matches with its compiled version from package.json. 
Looking at the documentation for grunt version (https://github.com/kswedberg/grunt-version#default-options) it looks like your file has to have `var version = <some string>` somewhere in it so that the task can replace the text. We could normalize this to simply be:
````coffeescript
package_version = '0'
````
to avoid confusion.