Update 'once' listeners to accept a block argument

One-time listeners now accept an emitted callback to match the
behavior of persistent listeners.
Merge pull request #5 from invisiblefunnel/emit-callbacks

Update 'once' listeners to accept a block argument
all streams inherit default connection window
refactor compressor to use Buffer
emit SETTINGS as part of connection header
fixup error initialization
update example client/server
NPN friendly client
additional interop examples
NPN negotiation support for example server
fix settings examples in readme
version: http2-06, hpac-03