Generate Dummy App for Test Suite

This change removes the dummy Rails app used to run the run the test suite. Instead we now create a dummy application on the fly using a Rails template and the `pageflow:install` generator instead. Advantages:

* Test coverage for the generator ensuring that it successfully creates a working Pageflow application
* Less coupling to Rails versions. Test suite can now be run against Rails 4.0 and 4.1

In addition, the included `pageflow-support` gem allows to also use generated dummy applications to test Pageflow extension gems.