Prep for next feature
ensure.signature() can display custom messages
Size.add displays custom error message for incompatible types
'oop.js' module has functions for determining object names
ensure.js uses oop.js
Size's 'incompatable type' error uses oop.js
ensure.signature() no longer supports custom messages
INTEGRATE: Size displays error when used with incompatible types

* dev:
  ensure.signature() no longer supports custom messages
  Size's 'incompatable type' error uses oop.js
  ensure.js uses oop.js
  'oop.js' module has functions for determining object names
  Size.add displays custom error message for incompatible types
  ensure.signature() can display custom messages
  Prep for next feature