benchmark: Add some path benchmarks for #1778

Path functions being benchmarked are:
* format
* isAbsolute
* join
* normalize
* relative
* resolve

PR-URL: https://github.com/nodejs/io.js/pull/1778


Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>