Shush Mime::JSON deprecation. Switch to backward-compatible Mime[:json]

Author: jeremy

lib/jbuilder/jbuilder_template.rb

@@ -170,7 +170,7 @@ def _render_active_model_partial(object)
 
 class JbuilderHandler
   cattr_accessor :default_format
-  self.default_format = Mime::JSON
+  self.default_format = Mime[:json]
 
   def self.call(template)
     # this juggling is required to keep line numbers right in the error