removed the old signup and signin pages which was not in use (except if you tried to post a new link without being logged in, then you got redirected to that login page)
removed the last few references to the old sign in flow - (trying to up up vote comments without being signed in etc.)
also unified all references to /sign-in to use the getSigninUrl()
Set fromWhere session to return to the current page after successful login.
(eg. if i go to /submit without being logged in, I will be moved to the the login page, and after a successful login i will be transferred back to the submit page)
Merge pull request #376 from niklasdstrom/remove-unused-signin

Remove unused signin