Monty

1. Py3 only version.

1. MSONable now supports Enum types. (mkhorton)

1. Revert py27 incompatible fmt spec for loadfn and dumpfn for now. This is
a much less common use case.

1. Checking for extension type in loadfn and dumpfn now relies on ".json",
".yaml" or ".mpk". Further, now ".yml" and ".yaml" are both recognized as
YAML files. (clegaspi)
2. A fmt kwarg is now supported in loadfn and dumpfn to specify the format
explicitly. (clegaspi)

1. Bug fix for invert MSON caused by `version`.

1. Support for nested MSONAble objects with MontyEncoder and dumpfn.
(davidwaroquiers)
2. Add version to MSONAble. (mkhorton)