Remove docs/release section from the Bio-Formats repository

The download page generation is maintained under a separate
openmicroscopy/ome-release repository so this folder is not needed anymore.
Remove docs/release from the Travis build job
merge develop -D org -I include -E exclude: PR 528 (Tile performance improvements for VMS and NDPI)
merge develop -D org -I include -E exclude: PR 836 (Update JPEGTurboServiceImpl.java)
merge develop -D org -I include -E exclude: PR 857 (Initial support for Zeiss .lms files)
merge develop -D org -I include -E exclude: PR 858 (Initial support for Veeco AFM data)
merge develop -D org -I include -E exclude: PR 859 (Assorted metadata/tile parsing fixes)
merge develop -D org -I include -E exclude: PR 865 (Remove docs/release section from the Bio-Formats repository (rebased onto develop))