improve redirect after login

[deiucanta]

Instead of checking for explicit routes, this tries to exclude any unwanted routes and store anything else. All of the following 5 conditions have to be met in order to save the current path

1. User must not be logged in (saves some resources)
2. Route must not be /login (you don't want to get back to login after login)
3. Route must not be /signup (same reason as above)
4. Route must not start with /auth (same reason as above)
5. Path does not contain a dot (this usually matches a file and you don't want to be redirected to favicon.ico)

[vincentbriglia]

since passport is prevalently used, wouldn't https://github.com/jaredhanson/connect-ensure-login be a better option ?

[sahat]

Thanks for the pull request and sorry about the delay in merging it.