renamed sign in  module and added it to Rspec config file

Per your notes on this commit https://github.com/jpalmieri/blocitoff/commit/9b683a96ddf7f6221c1e83997d50aa21423429c5#commitcomment-8862903

Oh yes, that's a good thought. Devise's `TestHelper` uses that method name https://github.com/plataformatec/devise#test-helpers

It looks like it'll be OK though as I don't think the feature specs are using Devise's `TestHelper`, which is meant for use in controller specs.

If you wanted to check for sure that nothing else has defined a `sign_in` method, comment out the `sign_in` method definition in `SignInHelper`, then run the specs. If nothing else has defined the `sign_in` method then `NoMethodError`s should be raised.