Rebase pull benlangfeld#21 and fix Rails 4 compat

lib/mobile-fu.rb

@@ -168,41 +168,27 @@ def mobile_exempt?
   end
 end
 
+# the following code are obtained from https://github.com/cannikin/format_fallback
 module ActionView
-  class PathSet < Array
-
-    def find_with_default_template(path, prefix = nil, partial = false, details = {}, key = nil)
+  class PathSet
+    def find_with_default_template(path, prefix = nil, partial = false, details = {}, keys = [], key = nil)
       if prefix == "layouts"
         # Layouts have their own way of managing fallback, better leave them alone
-        find_without_default_template(path, prefix, partial, details, key)
+        find_without_default_template(path, prefix, partial, details, keys, key)
       else
         begin
-          find_without_default_template(path, prefix, partial, details, key)
+          find_without_default_template(path, prefix, partial, details, keys, key)
         rescue MissingTemplate => e
           raise e if details[:formats] == [:html]
           html_details = details.dup.merge(:formats => [:html])
-          find_without_default_template(path, prefix, partial, html_details, key)
+          find_without_default_template(path, prefix, partial, html_details, keys, key)
         end
       end
     end
     alias_method_chain :find, :default_template
-
-  end
-
-  class Resolver
-
-    def cached(key, prefix, name, partial)
-      return yield unless key && caching?
-      cache_content = yield
-      if cache_content.empty?
-        []
-      else
-        @cached[key][prefix][name][partial] ||= cache_content
-      end
-    end
-
   end
 end
+# end of code obtained from https://github.com/cannikin/format_fallback
 
 if Rails::VERSION::MAJOR < 3
   ActionController::Base.send :include, ActionController::MobileFu