Update to HTTP/2 Draft 10 and HPACK Draft 6.

Closes issue #691 

Addresses changes between drafts:
  * change id to `h2-10`
  * add frame padding, etc.
  * renumbering of frames, and settings ids.
  * flattened huffman into a single class as there's only one table
  * new opcode in hpack for table size changes
  * enforced unknown frame and setting ids are disallowed

#### Note!

Setting ids are no longer compatible on the wire between SPDY and HTTP/2.  The impl of HTTP/2 converts in and SPDY ids for the two settings renumbered.

  * `SETTINGS_MAX_CONCURRENT_STREAMS` in SPDY 4; in HTTP/2 3
  * `SETTINGS_INITIAL_WINDOW_SIZE` in SPDY 7; in HTTP/2 4