fix root path and tests

app/models/merged/shared_base.rb

@@ -11,7 +11,7 @@ module Merged
         raise "#{full} contained #{got.class}, not Array" unless got.class == Array
         got
       end
-      loaded_files.sum
+      loaded_files.first + loaded_files.last
     end
   end
 end

app/models/merged/view_base.rb

@@ -5,7 +5,7 @@ module Merged
   # and the fact that they persist in ActiveYaml
 
   class ViewBase < ActiveBase
-    set_root_path Merged.data_dir
+    set_root_path Rails.root.join(Merged.data_dir)
     include ActiveHash::Associations
 
     belongs_to :image , class_name: "Merged::Image"