[pony-build] Latest push--pony client work

[Jack Carlson]

http://github.com/JackCarlson/pony-build/commit/6d7ab7d098b0b2bb6afda37d323116831a8d8243

On my pony-client_rework branch.  Commit message goes over the juice details, feedback on the general functionality would be appreciated.

Next, need to fix a few bugs I've found already, this doesn't support overriding variables in the build script via the command line, I think tags are broken, etc.  So yes, a ways to go yet, but, progress!

-Jack