will redirect users if they come from community site using /?action=showlogin
move referer from callbackURL to state

- Revert back callbackURL
- set referer to 'state'
replaced wp_get_referer() to $_SERVER['HTTP_REFERER']

wp_get_referer() didn't captured referer from outside e.g:
community.topcoder.com
removed "echo" which was used to debug
Merge pull request #251 from topcoderinc/I-114441-custom-callback-login

I 114441 custom callback login