Remove bootstrap bower dependency

[ArekSredzki]

The bootstrap bower package isn't a literal dependency for this package.
With the current spec, if a developer chooses to use one of the many other ways of using bootstrap (such as bootstrap-sass-official + angular-bootstrap in my case), your explicit requirement spec causes headaches.

Note: while recent versions of bower have support for ignoring a particular dependency, wiredep does not support this so the problem is still present.