feature: cleaner cluster launch exit status

exiting with 0 status instead of 1 when launching a cluster that is
already launched.

This addresses https://github.com/infochimps-labs/ironfan/issues/343

Squashed commit of the following:

commit d84cd17869759aded212ba9e2ee57332a533958b
Author: Josh Bronson <josh.bronson@gmail.com>
Date:   Mon Feb 24 17:38:54 2014 -0600

    Version bump to 5.0.10

    Change-Id: I01622f2880d61aca0d7d2c4b06bf29df161fec89

commit c23ef64934efbeab0219a74ca8b931c7671e315e
Author: Josh Bronson <josh.bronson@gmail.com>
Date:   Mon Feb 24 17:38:37 2014 -0600

    exit status 0 instead of 1 when machines already launched

    Change-Id: I1a85c4c8f7d35fad9f56cf556fe5b0b7b9dbbe96

Change-Id: I0556717172cc8836ead1976e1b1b52e260f197b9