test_decrypt_keymaterial implemented
added some new metadata to fields; added new invalid HashAlgo to use as an initial value
implemented RFC 4880 String-to-Key key derivation function, which turns out to be a pretty stupid algorithm.
added a new field for encrypted key material so decrypted and unencrypted material have a canonicalized location
following RFC 4880, implemented key decryption
didn't need to truncate the key as the key derivation method is now returning one of an appropriate length
fix for Python 2.x because integer division is stupid
Merge branch 'feature/encrypted_key_decryption' into develop