Add methods to check subscription status.
Add public methods that only take address.
Fix the $member_info checks in isSubscribedMember() and isUnsubscribedMember()
 * check isset on the status key f  $member_info. We already know member_info itself is set.
 * strict equality when checking the value of the status key.
Merge pull request #3 from isaacgrant/charleswaddell-check-unsubscribed-member

Fix the $member_info checks in isSubscribedMember() and isUnsubscribedMember()
Merge pull request #8 from charleswaddell/check-unsubscribed-member

Add methods to check subscription status.