Use Github tar.gz instead of cloning the repo for the stable B-F

This change should speed up the installation time of Bio-Formats using `brew install bioformats`. Cloning the repository only makes sense for `omero.rb` since GH archives don't include the submodules.

Once this change is merged, any veto to opening a PR against the main homebrew repository to register bioformats.rb?

/cc @melissalinkert