added a clear link

Attempts to resolve #56 issue.

This works and is clearing the facets out, but - 

There are several issues that I was not able to figure out, and I think the solutions I have for them could be a little hacky. Open to suggestions on how they can be better - there are TODO comments in the code. I'm new to this tech stack, so please advise wherever possible.

Thanks for the bitesized tag! It was really helpful to find pieces that I could actually work through and understand.
You can bind to a selector event if doesn't exist, which is probably what you want here: https://github.com/flightjs/flight/blob/master/doc/base_api.md#this.on (see the part about the handler being an object)