Add a header to keep track of stream timeouts.

Add a method to kill sessions to a given host:port
pair.
zlib version up (to 1.2.8)
Merge pull request #8 from morodomi/master

zlib version up (to 1.2.8)
Merge branch 'master' of https://github.com/sorced-jim/SPDY-for-iPhone

Conflicts:
	SPDY/SPDY/SPDY.h
	SPDY/SPDY/SpdySession.m
	SPDY/SPDY/SpdyStream.h