Updating mod_roster to allows ejabberd to store rosters in redis.
Roster is stored in a redis hash as following:

{
  "rosterusers::username1": [
				{"user2@server2": "nick2::subscription2::ask2::askmessage2::group2"},
                                {"user3@server3": "nick3::subscription3::ask3::askmessage3::group3"},
                                {"user3@server4": "nick4::subscription4::ask4::askmessage4::group4"}
			    ]

}
Fix error in get_in_pending_subscriptions
Allowing ejabberd to connect to redis proxy nutcracker (ex twemproxy)
Enabled connection to redis with a password
Fix invalid argument error when askmessage field of the roster is empty
Sets default redis password value to none.
Fix item deletion from the roster