mass exploitation plugin for MIRV

This is a mass exploitation plugin for MIRV. Usage mode is simple:

1. load mass
2. configure an exploit
3. use mass command and it will launch the configured exploit in the background for each target specified.

It is related to the MIRV pull request https://github.com/rapid7/metasploit-framework/pull/1182 and was meant to quickly deploy to all hosts.

Not dissimilar to the [RAPID FIRE PSEXEC FOR METASPLOIT](http://www.room362.com/blog/2010/9/12/rapid-fire-psexec-for-metasploit.html)