Cleaned up the agument parsing and added support for excluding files/folders.

BUG=angle:552

Change-Id: I6dcf965f9b92ce4aa1c0b64bd4f9a0420883bcf6
Reviewed-on: https://chromium-review.googlesource.com/185204Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>