Add an option to run a check implemented in ruby in a forked process ins...

...tead of a using sh -c for performance gains

I tried this out and it works and is around 20x faster than IO.popen.  We'd have to add a config option to all of our checks.  What do you guys think of this solution? 

@obrie @deanxorr @will-ob  @mattcarbone @tannerburson