Configure use of fs.watch

I have a use case where I want to quickly add an item to the queue from a different process, and don't want to have the queue hang around forever (due to fs.watch). I've added a configuration to support this feature. This should be backwards compatible with existing code.

I also added a couple methods on to be able to stop a queue in progress, and determine if it is running.

I fixed the README documentation, mostly spelling, but some implementation.

I fixed some of the jslint errors I was seeing; added flags to ignore the rest.