Tweak README to introduce more basic blocks first
Tweak README to introduce more basic blocks first

As suggested by @monkbroc in https://github.com/barsoom/attr_extras/issues/9#issuecomment-74269039.

tanmay3011/attr_extras,blackchestnut/attr_extras,scalp42/attr_extras,barsoom/attr_extras,JuanitoFatas/attr_extras