Add Sereal as a serialization library:

Sereal is, by far, the best serialization library we currently have.

It's new, faster than all others, maintains more compatibility, written
by #p5p hackers & co., is used at Booking.com, and has already been
ported to multiple others languages (such as Go).

You can read more about it here:
http://blog.booking.com/sereal-a-binary-data-serialization-format.html
Merge pull request #20 from xsawyerx/add-sereal

Add Sereal as a serialization library: