Add a new PRIORITY frame to allow reprioritization.
Add a little text about reprioritization.
Rather than use type 0x09, use 0x02 which is free (used to be SYN_REPLY)
Rookie error: removed wrong </section> tags. Fix it.
Update Changelog.
IETF rookie error: need to update IANA considerations section.

Added the new PRIORITY frame there too.
Merge pull request #111 from willchan/Priority

Priority frame definition