Adding support for OSX by including mariadb-5.5.34 built via homebrew

Don't merge this yet -- I have the unit tests passing, but haven't tested out the functionality for real yet. Just wanted to let you know this is coming shortly.

Since quite a few OpenMRS developers (including myself) are on OSX, we need to add OSX support before we can really try to scale up our usage of this tool.

Since there are no prebuilt mariadb4j binaries for OSX, I built it myself using homebrew, following the hint here: https://mariadb.com/kb/en/building-mariadb-on-mac-os-x-using-homebrew/

One issue is that I got 5.5.34 (the latest), whereas the linux version is 5.5.33a. My preference would be to upgrade the linux version to match the OSX one, but I'm open to suggestions.

Another note is that on OSX, bin/mysql_install_db is a symlink to scripts/mysql_install_db. (In fact I'll document this in the readme file in another commit.)