Replace IrisCouch logo with Nodejitsu since IrisCouch has been part of Nodejitsu since May 2013.

@izs Sending this in the form of a pull-request since that is what @jhs said you asked for. I don't have any of the dependencies installed on my dev system (e.g. `elasticsearch`) so if you could review this for actual appearance I'd appreciate it -- e.g. I think `32x115` isn't the correct aspect ratio for the Nodejitsu logo.

@3rd-Eden or @swaagie can help out here. I'm just getting the ball rolling.