Add benchmark script for pencode.pencode()
Add benchmark script for pencode.pencode()

Baseline on a MBP A1389, i7-4750HQ CPU @ 2.00GHz, Ubuntu 17.10 x64,
Python 2.7.14, kernel 4.13.0-36-generic

pencode: Mean +- std dev: 95.8 ms +- 1.2 ms

lordmauve/chopsticks,lordmauve/chopsticks