Fixing imglib scifio github link (rebased onto develop)


This is the same as gh-1184 but rebased onto develop.

N.B. 5.1 docs build will still be yellow because the doxygen docs don't exist yet.

----

This should make the BF doc builds green again by fixing the ImgOpener link on http://www.openmicroscopy.org/site/support/bio-formats5-staging/users/imglib/index.html