Use newer recast to support source maps

This PR should look [familiar](https://github.com/square/es6-arrow-function/pull/4) :)

The source maps are pretty good fidelity, too: [here's an example](http://sokra.github.io/source-map-visualization/#base64,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,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,Y2xhc3MgQW5pbWFsIHsKICBzYXlIaSgpIHsKICAgIHJldHVybiAnSGksIEkgYW0gYSAnK3RoaXMudHlwZSgpKycuJzsKICB9Cn0KCmNsYXNzIERvZyBleHRlbmRzIEFuaW1hbCB7CiAgdHlwZSgpIHsgcmV0dXJuICdkb2cnOyB9CgogIHNheUhpKCkgewogICAgcmV0dXJuIHN1cGVyKCkgKyAnIFdPT0YhJzsKICB9Cn0KCmFzc2VydC5lcXVhbChuZXcgRG9nKCkuc2F5SGkoKSwgJ0hpLCBJIGFtIGEgZG9nLiBXT09GIScpOwo=).

(as an aside, I'm excited about this because now the es6-arrow-function, es6-class, and the Recast branch of es6-module-transpiler now have the same public API and should be easy to chain!)