This adds an installer for RBTools on MacOS X, which bundles the command

line utilities and the modules for both Python 2.6 and 2.7, both of

which are standard on modern versions of MacOS X.
The installer is built with the build-mpkg.sh script, which will

generate the appropriate builds for Python 2.6 and 2.7 versions, and

assemble all the pieces into a standard .pkg file that can be

distributed.
Currently, attempting to install this package will result in a complaint

about it not being signed, making it difficult and scary to install.

This will be fixed when we have the ability to sign the package, which

will happen prior to the package's official release.

Built an installer and tested it in a VM. Successfully installed a build

of RBTools, and had access to the Python modules from both Python 2.6 and 2.7.
I was able to build this inside and outside of a virtualenv, without any path

distortion.