benchmark: allow compare via fine-grained filters

Before this commit, only benchmark targets defined in Makefile could
be used. This commit allows execution of common.js directly and
passing of filter arguments directly, allowing you to run either a
subset of benchmarks or a single specific benchmark for comparison.

PR-URL: https://github.com/iojs/io.js/pull/711


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>