Add support for setting HTTPS

[Chowarmaan]

Most of the Google CDNs now have the ability to set the link using HTTPS. When the bower_components are converted, it would be nice to have an option to use HTTPS if supported, or to set it on the CDN as a flag.

Source

<script src="bower_components/angular/angular.js"></script>

becomes:

<script src="//ajax.googleapis.com/ajax/libs/angularjs/1.4.5/angular.min.js"></script>

However, Google supports

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.5/angular.min.js"></script>

Either test the URL to see if https is valid for the script, or add a flag to allow this. I know on my own urls, I could do this by returning the HTTPS, but it would be nice to use the default CDNs so as to not have to keep the versions up to date etc...