Add support for MaxStartups and MaxSessions in sshd_config

MaxStartups and MaxSessions control how many connections can be made to a ssh server.
Corrected faulty commented value for MaxStartups.
Improve validation of sshd_config_maxstartups and add spec tests
Support Ruby v2.1.0
Merge pull request #99 from ghoneycutt/maxstartups_and_maxsessions

Maxstartups and maxsessions