add feature: specify rule tags in any cookbook's .foodcritic file

Hi Andrew --

This patch adds a feature that we need at the Gap online: in any cookbook, you can create a .foodcritic file with rule tags in it, and foodcritic honor the tags as if they were set on the command line or in inline comments.

Why we want this: we'd like Jenkins to run foodcritic with "--epic-fail any". Like many shops, we've got a mix of our own custom cookbooks and 3rd party cookbooks. We do fix our own cookbooks based on foodcritic, but we don't want to be in the business of fixing other peoples' cookbooks.

By simply adding a .foodcritic file to a cookbook, we can squelch foodcritic on cookbooks we don't own.

In my change, I've done my best to conform to your coding style, and have added a cucumber test.

Thanks for your time!

-Steve Abatangle
steve_abatangle@gap.com