updated copyright year

The 2010 made me think that the project was abandoned. Also, arbor.js writes that it's based on springy. Only now that I take a closer look I see that there are recent commits.
added done callback to renderer start method.

The done callback existed in the ForceDirected layout start method, but no one passed that in. Maybe I don't understand how it's meant to be used? Or something was lost on the way with refactorings in springy? Anyway, with this change it's possible to call the Springy.Renderer start() method with a done callback. Please accept it, or document how it's meant to be used. Thanks ;-)
Documented that start() is silently ignored if running.
Render start and stop callbacks for all cases.

Rendering can happen on demand (by calling start()) but also when adding/removing nodes and relations. I also need to be informed when rendering starts in my use case. I have a re-arrange button that needs to be toggled whenever rendering is in progress, and with these events it's nice and clean.
When the event callbacks are passed in to the Springy.Renderer start() method only (as in my previous commit) then all the other cases are left out (adding/removing nodes/relations).
Merge remote-tracking branch 'fabiankessler/master'

* fabiankessler/master:
  Render start and stop callbacks for all cases.
  Documented that start() is silently ignored if running.
  added done callback to renderer start method.
  updated copyright year
Switch order of onRenderStop and onRenderStart to preserve backwards compat
Bumped version