Turn off noisy RSpec warnings

https://github.com/everydayrails/rails-4-1-rspec-3-0/issues/13
Merge branch '02_setup' into 03_models
Merge branch '03_models' into 04_factories
Fix typo in contact_spec descriptions

https://github.com/everydayrails/rails-4-1-rspec-3-0/issues/4
Merge branch '04_factories' into 05_controller_basics
Use not_to for consistency with book and RSpec documentation

https://github.com/everydayrails/rails-4-1-rspec-3-0/issues/3