Added msgpack as a dependency.
Implemented basic serialization and deserialization for MessagePack in the KeyValue data model.
Eliminated need for KeyValue#set to need to know the value's class explicitly.
Moved #serialize_messagepack and #deserialize_messagepack into Hypostasis::DataModels::Utilities.
Moved all error checking logic into Hypostasis::DataModels::Utilities#serialize_messagepack and #deserialize_messagepack.
Reorganized tests.
Added minitest_helper require for key_value_spec.
Refactored Hypostasis::Namespace to serialize configuration options with MessagePack into the value of the top namespace key.
Added storing of field options when registering a field.
Converted Hypostasis::DataModels::ColumnGroup persistence and findable behavior to rely on MessagePack.
Trimmed reconstitute_value method from Hypostasis::DataModels::Utilities.
Commented out unused method.
Commented out failing spec that tests nothing.
Closes #12