Make using __slots__ in generated code optional

f^
Add a function to expose the name of an enum, given the value
Don't generate the same __contains__ method for every field in the protobuf
Merge pull request #20 from dowski/master

Fix for enum values as defaults
Merge pull request #21 from wmoss/master

A few small things
Bump the version number

* Also remove the download url, since it's not valid any more
Bump the version number again
Make the method from e6831e for enums a classmethod
Update readme--stable enough to use.
Drop some unused code