Include Mac OSX dependancy and build instructions in Install file

[cdu13a]

The Install file has good instructions for building flare on various platforms. It would be nice if there was good instructions for building flare and installing build dependencies on Mac OSX as well.

I think it would be good to have easy to follow instructions for all the main platforms flare can run on. That way barriers to contribute can be minimized for those people who are not programmers, but are capable in other areas such as, creating art assets, quests, etc.

[dorkster]

Migrated to https://github.com/clintbellanger/flare-engine/issues/1124