gem runtime

[Charles Lowell]

As I'm working with it, I'm not really digging the organization of the
prototype plugin. I think it was a mistake for me bundle the command
line tools and the runtime ruby lib as a single gem. It's just to
awkward to get the right gems bundled into the .hpi without pulling in
all the command line utilities and their dependencies.

I think they can live in the same repo (jenkins-plugins), but I'll
split them into two separate gems in tools/ and runtime/


cheers,
Charles