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

Nice one spotting the filename fix.

Next time when running RSpec, try `rspec` instead of `rspec spec` to save 5 whole keystrokes, it ought to default to looking for the specs in that directory.