Switch to using UNIX timestampts
Decode secret before using it

Closes #5
Use the attr_reader
These helpers are really not required
Implements new format
Get to green
Remove obsolete pending specs
Removes Yajl dependency
More explicitely test that enforce_ttl can be set in the verify call
Fixes usability issue on verifiers and ttl

Addresses https://github.com/hgmnz/fernet/pull/3
Allow setting enforce_ttl in verifier block
Removes support for custom verifications - should be done externally
Ruby 1.8 hash syntax