RPS: devise functionality user sign-in, sign-out, sign-up from "main.html.erb"

modified main.html.erb to include functioning features of user sign-in, sign-out, sign-up, current-user display using devise.
We have made some adjustments in Devise on the main page.

I have incorporated Devise into the navigation bar and on the main page. Everything works as far as sign up, log in and log out.
Merge pull request #62 from seanlarge/feat_max_add_devise_functionality_main

RPS: devise functionality user sign-in, sign-out, sign-up from "main.htm...