test: create temp dir in common.js

Move creation of temporary directories for tests
out of the Python harness and into common.js. This
allows all tests to be run reliably outside of the
Python wrapper.

PR-URL: https://github.com/nodejs/io.js/pull/1877


Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>