Version 5 0 4 release

This is the update to bring the github version into line with the active 5.0.4 version release.

To review check Home page, Getting Started Version 5, Importing Version 5, Resources and Previous pages. Make sure all 5.0.3 references have been updated to 5.0.4.

Will be viewable at: http://snoopycrimecop.github.io/ome-help/ 
:+1: Changes to `_config.yml` will need to go in before we customize `openmicroscopy` and `snoopycrimecop` to deploy at `help.openmicroscopy.org` and `help.staging.openmicroscopy.org`. Do you see other planned changes for this file?