[StarCluster] shout out to StarCluster

[Joydeep Sen Sarma]

hey devs,

we are using StarCluster for our auto-scaling hadoop clusters. a big
thanks for a cool piece of software. more here:

http://www.qubole.com/blog/index.php/first-auto-scaling-hadoop-hive-clusters/

we owe some contribs back - i think there was a request to add the
userdata file option (we did that internally). a few other things we
did that might be useful:
- ability to override arbitrary config values from command line (many
parameters have become dynamic for us)
- a bunch of stuff around security groups (permissions block takes
explicit user+group pairs)

one general observation was that StarCluster outputs are very human
friendly - but not that machine friendly :-) - we added a few commands
just to get some json printfs out.

- joydeep