added the ability to control the accessibility level for each value. see this for more details on why it is important: https://blog.loom.com/how-we-fixed-the-ios7-forced-logout-bug-thats-been-plaguing-so-many-apps/
enabled PDKeychainBindings to support accessibility per value.
added a missing method...
Merge pull request #10 from yosit/master

added the ability to control the accessibility level for each value.