Bump grunt-usemin version.

Update Gruntfile config for compatibility
Remove escaped backslashes in src attributes

The escaped backslashes were causing grunt-usemin to replace the
filenames with the revved ones. The following RegEx was used
/(images\\?\/.*?\.(?:gif|jpeg|jpg|png|webp|svg))/gm
Update usemin task:

1. Update images with the correct rev number
2. HTML task check file 2 levels deep
3. HTML task replaces revved filenames for object tag and contains
defaults taken directly from gurnt-usemins fileprocessor.js so
they are not overriden
Inject dependencies as string to prevent them from being swallowed
by the minifier
Add grunt-replace to automatically assign Google analytics key during build
Stub out a main controller and view even though it's never used
Minor updates