feat(rxBreadcrumbsSvc): Add a `setHome` method

Closes #231

This PR does two things:

 1. A new `rxBreadcrumbsSvc.setHome()` method to change the first
 breadcrumb
 2. For the `ghPages` environment, it uses that method to give us the
 right URL at the top of the app
Merge pull request #487 from rackerlabs/i231_breadcrumbs_home

feat(rxBreadcrumbsSvc): Add a `setHome` method