Bump length field to 24 bits, and up max frame size to 2^14

We won't support frames larger than 2^14, for the sake of sane
multiplexing and prioritizaiton.
Add some missing semicolons
Handle SETTINGS_MAX_FRAME_SIZE
Remove END_SEGMENT
Window updates of 0 are illegal
Remove the reference set
Second HEADERS without END_STREAM is illegal
Update version number and references

Don't update HISTORY.md or the code coverage stats yet, as the new draft
isn't actually out yet!
Simplify frame length serialization/deserialization
Remove debugging code
Remove nul-concatenating of headers
Do not copy into the dynamic table from the static table
Swap static and dynamic tables
Update HISTORY
Merge pull request #26 from todesschaf/wip/draft14

Update to draft14
Don't allow invalid incoming stream IDs
Close all streams in a connection when it goes down
Use 'NO_ERROR' as the error in Stream.reset() if none was passed
Make Stream._ended public (Stream.ended), so users may rely on it

'ended' is only true when the stream was ended by END_STREAM and
not due to other means (such as RST_STREAM).