adding ruby tag to code blocks

docs/general/passing_arbitrary_options.md

@@ -2,7 +2,7 @@
 
 Let's say you have a basic Post Controller:
 
-```
+```ruby
 class PostController < ApplicationController
   def dashboard  
     render json: @posts
@@ -12,7 +12,7 @@ end
 
 Odds are, your serializer will look something like this:
 
-```
+```ruby
 class PostSerializer < ActiveModel::Serializer
   attributes :id, :title, :body
 end
@@ -23,7 +23,7 @@ into the serializer. Here's what you would do:
 
 ### posts_controller.rb
 
-```
+```ruby
 ...
   def dashboard  
     render json: @posts, user_id: 12
@@ -33,7 +33,7 @@ into the serializer. Here's what you would do:
 
 ### posts_serializer.rb
 
-```
+```ruby
 ...
   def comments_by_me  
     Comments.where(user_id: instance_options[:user_id], post_id: object.id)