remove es2015.promise from tsconfig libs
remove es2015.promise from tsconfig libs

- this isn't actually necessary, it's an artifact from when I was
  putting the build script together in .ts before converting it back
  to .js

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