Changed intro text and moved/added to explaination about SSH requirements.

Signed-off-by: Neil Levine <neil.levine@inktank.com>
Merge pull request #3 from nwl/readme-updates

Changed intro text and moved/added to explaination about SSH requirements
mon: implement 'destroy'

Remove the mon from the cluster, stop the daemon, and then remove the
directory.

Signed-off-by: Sage Weil <sage@inktank.com>