Dropdown with number as selectedItem throws warning

[alissa9090]

The current version of Dropdown accepts selectedItem prop with the following type:
selectedItem: PropTypes.oneOfType([PropTypes.object, PropTypes.string])

In our project (and I think this is a common case for many projects) selectedItem is either id of some entity or an enum value. And those value may have number type quite often. It causes warning in a console:
Warning: Failed prop type: Invalid prop 'selectedItem' supplied to 'Dropdown'.

I would suggest to remove type restriction for selectedItem.