add to_msgpack method to Ruby Core APIs.
Thank you for this PR. If we're going to add #to_msgpack I think it must include support for adding the method to your own classes, like suggested in #13.
The idea right now is to try to merge this gem into msgpack/msgpack-ruby, and that means supporting everything that that gem supports, including this. I'll have to see if I'll merge this PR or implement it as part of the merge.
this PR cotains very simple case only. this PR don't contain one argment with calling to_msgpack method.
This will happen in msgpack/msgpack-ruby#33
:+1:
:+1:
Any chance to have it mainline?