Allow html files to be served by asset-manager, add angular support

Asset-manager will now serve html files from the html directory.
It will also behave specially to not mangle filenames when minifying files in a directory named "angular"
Remove skipMangle for angular files. This needs more discussion and will go in a separate branch.
Merge pull request #38 from fs-webdev/html-angular-support

Provide support to serve html from asset-manager