Add `brew tap homebrew/science` to the Homebrew installation page
Simplify PDF to remove warning
Merge pull request #450 from rleigh-dundee/python2.6-minver

omero: Python 2.6 is the minimum supported version
Merge remote-tracking branch 'origin/develop' into rebased/develop/hdf5_tap

Conflicts:
	omero/sysadmins/unix/server-install-homebrew.txt
merge develop -D org -I include -E exclude: PR 491 (Add `brew tap homebrew/science` to the Homebrew installation page (rebased onto develop))
merge develop -D org -I include -E exclude: PR 518 (Add note for BF users redirected to upgrade (rebased))
merge develop -D org -I include -E exclude: PR 519 (Simplify PDF to remove warning)