Add note/link about cross-validation

https://github.com/ome/omero-wndcharm/issues/39
Add note about refreshing to see prediction results.

https://github.com/ome/omero-wndcharm/issues/41
Add note about deletes failing.

https://github.com/ome/omero-wndcharm/issues/42
Merge pull request #43 from manics/gh-pages

Documentation fixes from pre-release testing