Allow additional arguments to be passed to filters

I noticed `applyFilter` was not passing the additional arguments I was giving it. This commit fixes that. I've not unit-tested it (to be honest I had trouble getting grunt to work) but it appears to work in the project I'm using it in.

(On a completely unrelated note is there a reason to call it `applyFilter` vs `applyFilters` - which matches WordPress' `apply_filters()`?)