support for default values

[gcanti]

No description provided.

[ctrlplusb]

Hi;

Whilst you are making these changes could you add a cleanup for some useless artefacts from my PR.

https://github.com/gcanti/babel-plugin-tcomb/blob/master/src/index.js#L198
and
https://github.com/gcanti/babel-plugin-tcomb/blob/master/src/index.js#L205

The tcombLocalName parameters are useless. Sorry I was playing around passing through state as recommended by the babel-handbook, but it was a bigger change than I anticipated so I rolled back. These parameters slipped through the rollback though.

Thanks.

[gcanti]

@ctrlplusb sure, thanks