Fixes the dcdr-js client's file watcher

[stateoflux]

I discovered that the dcdr-js client was not responding to any changes made to the underlying decider.json file. The client was using node's fs.watch to implement its file watching capability, but turns out fs.watch is notoriously buggy. I've replaced fs.watch with the chokidar library (note this library used by many of the js build systems out there), which is a wrapper around the fs.watch but fixes its shortcomings. I've also written a unit test to cover file watching functionality.

[bshackelford]

Nice. Thank you.

[promiseofcake]

Thanks. Only question would be whether or not we want to commit package-lock.json since we aren't currently targeting builds > Node 6 for this repo. If we have use-cases for newer versions it might make sense to add them to build build matrix.

[stateoflux]

@promiseofcake I've removed the package-lock.json

[promiseofcake]

Thanks @stateoflux, I think if we are using this in newer node deployments we can also increment the build matrix / deprecate old builds if desired.