Add Watchman to the project

[yeah-sir]

Running the jest tests on the rules editor project issues a warning regarding watchman.

jest-haste-map: Watchman crawl failed. Retrying once with node crawler. Usually this happens when watchman isn't running. Create an empty .watchmanconfig file in your project's root folder or initialize a git or hg repository in your project.

Should we set up a watcher (using watchman) for this project to rebuild when any code changes are made? This will get rid of the jest warning as well.

More on watchman here: https://facebook.github.io/watchman/

[timjacobi]

#19 Disables the warning for now