Deprecate old hadoop_cluster api. Lay foundation of new clusters api. Update usage.
Add 'cluster delelte' command
Add support for 'cluster start' and 'cluster terminate' commands.
Add support for 'cluster status' command which shows the cluster state
(DOWN, PENDING, TERMINATING, UP)
show action is not needed. Will use list <id> instead.
Add support for 'cluster list' command.

It also supports showing a particular cluster by id or tag. You can also filter
by cluster state. I have used argparse to parse the command line arguments
instead of optparse. I will eventually migrate the whole codebase to use
argparse.
Pretty print the json result
Use label instead of tag.
Add support for 'cluster add' command.
Add support 'cluster update'
Only send the minimal payload
Add support for supplying the label while submitting commands.
Minor fixes: Remove unused import, add default for encrypted-ephemerals, whitespace fix.
Print error message and exit instead of raising exception.
Add docstrings for Cluster methods.
Fix bug where it was impossible to send False values for boolean options.

We only send the minimal payload while sending a create/update request.
This is because we don't want to change the already existing defaults.
So, I have set the default value for boolean types None (instead of False)
because if the default were False, it would be sent with every request
on account of being non-None. However, this made it impossible to send a
False value in a request. So, now I have added complementary options
which can be used to send a False value for these options.
Merge pull request #27 from mindprince/cluster-api

Add support for multicluster api