1.9.3-p194 :001 > cc = Campaign.first
  Campaign Load (6.1ms)  SELECT "campaigns".* FROM "campaigns" LIMIT 1
 => #<Campaign ...> 
1.9.3-p194 :002 > cc.tags
 => " health style" 
1.9.3-p194 :003 > cc.tags << " another"
 => " health style another" 
1.9.3-p194 :004 > cc.tags_changed?
 => false 
1.9.3-p194 :005 > cc.tags += " another"
 => " health style another another" 
1.9.3-p194 :006 > cc.tags_changed?
 => true