Adds default values to limits when the db does not have them

This prevents errors when doing rake db:setup (the db has still not
been created but the rails models are loaded)

app/models/debate.rb

@@ -147,7 +147,7 @@ class Debate < ActiveRecord::Base
   end
 
   def self.title_max_length
-    @@title_max_length ||= self.columns.find { |c| c.name == 'title' }.limit
+    @@title_max_length ||= self.columns.find { |c| c.name == 'title' }.limit || 80
   end
 
   def self.description_max_length

app/models/organization.rb

@@ -34,7 +34,7 @@ class Organization < ActiveRecord::Base
   end
 
   def self.name_max_length
-    @@name_max_length ||= self.columns.find { |c| c.name == 'name' }.limit
+    @@name_max_length ||= self.columns.find { |c| c.name == 'name' }.limit || 60
   end
 
   private

app/models/user.rb

@@ -144,7 +144,7 @@ class User < ActiveRecord::Base
   end
 
   def self.username_max_length
-    @@username_max_length ||= self.columns.find { |c| c.name == 'username' }.limit
+    @@username_max_length ||= self.columns.find { |c| c.name == 'username' }.limit || 60
   end
 
   def show_welcome_screen?