Implement a run() method for external usage

I wanted to be able to use my SiriProxy plugins outside of the normal SiriProxy context, pull request adds a run() method for that purpose. Accepts a string input, returns SiriProxy's response from any plugins. I've tested it with an IRC plugin.

require 'siriproxy/command_line'

siri = SiriProxy::CommandLine.new
puts siri.run("test siri proxy")