refactored tag definitions to declare errors at the top
refactored tag definitions to declare errors at the top

unified style across asset_tags.rb
raise early instead of long nested if blocks

kbingman/paperclipped,kbingman/paperclipped,radiant/radiant-clipped-extension,GarPit/radiant-clipped-extension,radiant/radiant-clipped-extension,GarPit/radiant-clipped-extension,saturnflyer/paperclipped,radiant/radiant-clipped-extension,radiant/radiant-clipped-extension