Automatically convert between camelCase and underscores (the other way around)

You added automatic conversion from underscores to camelCase in 2.1 (#31), but it doesn't seem to work the other way: converting camelCase to underscores. This way it is not possible to communicate with a server using underscores correctly without creating separate modell classes for incomming and outgoing communication.

Or am I doing something wrong? I am using it from Swift if it matters.