Ignore paths

did it on the plane, changed a bunch of stuff (sorry!), should be working, tests pass. plane is landing now so i have to stop.
I used `lodash`, which is a faster and improved `underscore`, instead of the `simplesets` library because it's more flexible and widely used. It's created by the same person who created jsperf. It's also great for making code more functional.

http://lodash.com/docs