Default value for Snippet#private

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/models/snippet.rb

@@ -20,6 +20,8 @@ class Snippet < ActiveRecord::Base
 
   attr_accessible :title, :content, :file_name, :expires_at, :private
 
+  default_value_for :private, true
+
   belongs_to :author, class_name: "User"
 
   has_many :notes, as: :noteable, dependent: :destroy