Omnibus fixes

This includes the commits from my previous pull request related to the UI and AMQP issues.

The fixes specific to this request:

* communicate to the user when the package can't be downloaded (right now it just bails silently)
* fix a spelling error
* provide a --no-test/-n option which does not run opscode pedant after installing erchef. This speeds up install time significantly if you're not interested in the test results.