message: Remove andThen
  It doesn't really do anything that map doesn't do already.
diff: @@ -46,11 +46,3 @@ export function map<T, R>(obj: Option<T>, f: (obj: T) => R): R | undefined {
  return undefined;
  }
  }
  -
  -export function andThen<T, R>(obj: Option<T>, f: (obj: T) => Option<R>): Option<R> {
  - if (obj != null) {
  - return f(obj);
  - } else {
  - return undefined;
  - }
  -}
  