Add --devel option to install the OMERO 5 via Homebrew

This PR fixes an issue reported in https://www.openmicroscopy.org/community/viewtopic.php?f=6&p=13350#p13332

Until we archive the OMERO 4.4 Homebrew formula, the OMERO 5 formula needs be installed by passing the `--devel` option (see http://ci.openmicroscopy.org/job/OME-5.0-merge-homebrew/).