Add BREW_OPTS variable to test devel/head Homebrew formulas (rebased onto dev_4_4)



This is the same as gh-814 but rebased onto dev_4_4.

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This PR will be tested in the [OMERO-homebrew-develop](http://hudson.openmicroscopy.org.uk/job/OMERO-homebrew-develop) job in conjunction with ome/homebrew-alt#22.