Moving some gems to the assets/dev group

Gemfile

@@ -127,7 +127,7 @@ group :development, :test, :assets do
 
   # Carte openstreetmap
   gem 'leaflet-rails'
-  gem 'rails-assets-leaflet.markercluster'
+  gem 'rails-assets-leaflet.markercluster', source: 'https://rails-assets.org'
 end
 
 group :assets do

Gemfile.lock

@@ -34,6 +34,7 @@ GIT
 
 GEM
   remote: https://rubygems.org/
+  remote: https://rails-assets.org/
   specs:
     actionmailer (4.2.7.1)
       actionpack (= 4.2.7.1)
@@ -452,7 +453,7 @@ DEPENDENCIES
   quiet_assets
   rack-livereload
   rails
-  rails-assets-leaflet.markercluster
+  rails-assets-leaflet.markercluster!
   rails-i18n
   redcarpet
   sass-rails