add tests for createTransform with primitive integer keys
add tests for createTransform with primitive integer keys

mobxjs/mobx,andykog/mobx,mweststrate/MOBservable,mobxjs/mobx,mobxjs/mobx,mweststrate/MOBservable,mobxjs/mobx,andykog/mobx,andykog/mobservable,andykog/mobservable,mweststrate/MOBservable