Convert pref btn group partial to haml

Just converting .erb to .haml

Also, found a subtle bug.  When the PreferencesController specs were run before the RestaurantsController specs, some of the RestaurantsController tests would fail.

Look at [this RSpec documentation](https://www.relishapp.com/rspec/rspec-rails/v/2-12-2/docs/transactions) for an explanation of why it happens and why the fix worked.

TL;DR:  Data created in ```before(:each)``` are rolled back; Data created in ```before(:all)``` are **not** rolled back.