Start adding benchmarks to pygolang.

Measure how much sync chan send/recv take and how much select takes for
synchronous channels. Also measure how much overhead @func adds at both
def and call times, and the overhead of defer compared to try/finally.
For std (non-gevent'ed) Python2.7 we are currently at:

	name         time/op
	go           91.6µs ± 1%
	chan         13.7µs ± 3%
	select       30.1µs ± 4%
	def          55.0ns ± 0%
	func_def     43.6µs ± 0%
	call         63.0ns ± 0%
	func_call    1.06µs ± 0%
	try_finally   136ns ± 1%
	defer        2.33µs ± 0%