All work and no play makes Jack a dull boy

Robots can now take a break and have #play functions instead of #work.
Internally they're treated the same, but it's a fun easter egg!

Example:

Cylon.robot({
  name: 'Jack',

  connections: [],
  devices: [],

  play: function play(my) {
    every((5).seconds(), function() {
      console.log("All work and no play makes %s a dull boy.", my.name);
    });
  }
});

I sincerely apologize for the repeated reference to The Shining, blame
@deadprogram.

Closes #189.