dependency optimisation

There are many ways to optimise the dependencies of this package.

1. react-dnd uses `lodash "^4.2.0"` so including `lodash.throttle "^4.0.1"` is a duplication of code
2. react-dnd uses `hoist-non-react-statics` "^2.1.0" while this package requires `"^1.2.0"`, so it's a duplicated version of the same library! Can it be upgraded to 2.x?

