Factor out the HTTP(s) server creation to another file, for easy embedding
Rename roboHydraHeadType to robohydraHeadType
Reorganise code a little bit

* Try to keep the main file, lib/robohydra.js, as the public-facing
  module with just the exports.
* Move the RoboHydra class to lib/RoboHydra.js.
Be more explicit about createRoboHydraServer's parameters

While at it, add embedded documentation for createRoboHydraServer.
Add quiet option to suppress console logging
Make command-line port have precedence over configuration file
Simple, manual testsuite for the command-line tool