Update framing section from HTTP/2

Ditch all the old artwork conventions and describe in the framing header section.
Purely editorial here.
Copies the HTTP/2 DATA frame section to SPDY.

* Preserves the MSG_DONE flag used for layering other protocols like WebSocket
* Removes requirement that DATA frames come _after_ HEADERS. Used to be a PROTOCOL_ERROR
* Removes requirement that DATA frames be sent for valid streams. Used to be a INVALID_STREAM error
Updates the HEADER+PRIORITY frame.

* Notably picks up the CONTINUES flag.
Update RST_STREAM

No major change. Just redid artwork.
Update SETTINGS frame.

* Notably changed the clear settings flag from 0x1 to 0x2 to conform
with HTTP/2 which makes FLAG_FINAL always be 0x1.
* Merges in the SPDY settings ids that differed. Notably the:
  - client certificate vector size ids
  - supported schemes
Update HTML/TXT
Update the PUSH_PROMISE frame from HTTP/2.

* Removes the specified behavior for FLAG_FINAL. I don't understand what the old behavior meant anyway.
* Removes the specified behavior around a RST_STREAM with FRAME_TOO_LARGE.
* There used to be more text around the stream id allocation, but it got removed and just linked to text elsewhere.
Update PING frame to match HTTP/2.

No substantial change, just editorial.
Update GOAWAY frame from HTTP/2.

No substantial change. Picked up a few editorial changes.
Update WINDOW_UPDATE to match HTTP/2.0.

Only editorial changes.
Fix </section> errors and generate HTML and TXT files.
Merge pull request #22 from willchan/Framing

Mostly editorial: Framing changes from HTTP/2