Delete dependency on OS X software installation

It doesn't make sense anymore to modify OS X settings from this library
as it should be concerned with setting up .dotfiles. In favor of using
the osxdefaults library for handling all software installation, remove
the logic and dependency on such installation.

Issue: #24
Update CHANGELOG for version 3.0.0

Final release of v3.0.0 (Beta release) is done and ready to ship.

Issue: #22