cache encoded_payload

Conflicts:
	lib/grocer/connection.rb
	lib/grocer/notification.rb
	lib/grocer/pusher.rb
cleanup notification cacheing encoded_payload
call destroy/disconnect in all places close
add delegates
don't throw away the ssl object, just disconnect
ring buffer that pops off the front not the end.
drops older entries
add can_read to allow non blocking read
pusher#push_and_retry