Add Alan Cutter as contributor
https://bugs.webkit.org/show_bug.cgi?id=106747

Patch by Alan Cutter <alancutter@chromium.org> on 2013-01-13
Reviewed by Eric Seidel.

* Scripts/webkitpy/common/config/committers.py:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@139575 268f45cc-cd09-0410-ab3c-d52691b4dbfc