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

Thanks for catching this. I ran the specs but it didn't show as failing because it wasn't actually running when I ran `rspec spec`. I figured out that it wasn't running because its filename doesn't end with `_spec.rb`.