Moving to https... fixing broken demo from #173

I added 'http' in #173 instead of using the scheme-less URI for the ressources. Apparently changing the scheme does have some pitfalls: 
Since the [demo](https://rawgit.com/ManifestWebDesign/angular-gridster/master/index.html) is using https, [firefox refuses to load ressources with http](https://support.mozilla.org/en-US/kb/how-does-content-isnt-secure-affect-my-safety) (unless explicitely told to allow it), therefore the page can't load the scripts which breaks the page. By using https it works both, on https and locally with ```file://``` (and http should be a problem either).

Sorry for that, couldn't test it, didn't expect it.