nimrod-lang: New and improved formulas

This pull request attempts to improve Homebrew's support for the Nimrod language by supplying two new and improved formulas. The explanation for the changes are in the commits themselves, and I'd also be happy to answer any questions about this here.
I'm going to have to think about how this will be possible here. Obviously the best way to test a package manager is to install a package with it, but the user may not want the package we choose to install for the test, and installing a package can potentially conflict with a user's installed packages.