Helper functions for use in development.


(use-hawk {:biff.hawk/keys [callback exts paths], :or {exts [".clj" ".cljs" ".cljc"], paths ["src"]}, :as sys})
A Biff component for Hawk. See

callback: A zero-argument function to call whenever a file is saved. The
          function is called no more than once every 500 milliseconds.
paths:    A collection of root directories to monitor for file changes.
exts:     If exts is provided, files that don't end in one of the extensions
          will be ignored.