Documents the mimetype of JSONP as application/javascript.
Fixes #188.

Parses Link headers and provides them as metadata to JSONP responses.

This also changes the JSONP response to use the {"meta": ..., "data": ...}
format, and so is backwards incompatible with previously written client code.
Changes in-development version number to 0.12.0-dev, because previous commit introduces a backwards-incompatible change.
PEP8 fixes.