[WIP] SPDY transport

[mcollina]

This pull request implements the SPDY transport session by using 'libchan-ref' for nested channels.

• [x] one directional channels
• [x] embed channels from the client to the server
• [x] embed channels from the server to the client
• [x] embed byte streams from the client to the server
• [x] embed byte streams from the server to the client
• [x] Update according to https://github.com/docker/libchan/issues/48#issuecomment-49929541
• [x] Interoperability test with Docker (https://github.com/dmcgowan/libchan/commit/3d21143c02e2510330e161585df34795f17a92be)
• [x] README
• [x] Use self-signed to generate server certificates on the fly, so users do not see we are on TLS.
• [x] go through all the FIXME and check if I'm mad
• [x] build examples
• [x] cleanup

Like I said, it's a WIP!