Problems leaflet-markercluster-rails and Rails 5

[mksndz]

I ran in to issues installing on a new Rails 5 app. It seems the leaflet-markercluster-rails gem does not yet work with Rails 5. See this PR on that repo which should address the issue

Until that fix is in place, I've make things work by including the JS from leaflet-markercluster in my assets after the blacklight-maps include.

[mejackreed]

Thanks for the heads up @mksndz !