Validate title, lat, lon on posts

app/models/post.rb

@@ -1,5 +1,8 @@
 class Post < ActiveRecord::Base
   belongs_to :feed
+  validates :title, :presence => true
+  validates :lat, :numericality => { :greater_than_or_equal_to => -90, :less_than_or_equal_to => 90 }
+  validates :lon, :numericality => { :greater_than_or_equal_to => -180, :less_than_or_equal_to => 180 }
   
   EARTH_RADIUS_METRES = 6378000