Compartmentalise icekit's bower deps

[markfinger]

Re: #286

The intention here is to keep all of icekit's deps within icekit itself, so that the project can define common url paths ("bootstrap/...", for example) without impacting on the admin's functionality.

Basically, we're using a .bowerrc file that tells bower to install all of the deps into a icekit/bower_components dir within icekit's static dir. All of the asset references have been updated to target that directory.

[markfinger]

Edit: all is well in docker-town

Looks like the docker build needs some tweaks. I had assumed that the setup-django.sh script was used in the build, but it looks like we need to explicitly add the various bits to the dockerfile.

Just waiting on travis to do its thing...

[coveralls]

Coverage remained the same at 73.719% when pulling a506d9f6799b28db48fc7e81b13ea02fd072a19c on feature/286-bower-install-icekit-deps into 8ae0e6540a0c7029fbec10e8abd0cbca7da0a120 on develop.