proptypes changes impacted inferno-compat

inferno-compat expects `proptypes` to export `proptypes.default`. Can you please export both directly and using default property?

```
> require('proptypes').default
undefined

> require('proptypes')
{ array: { [Function: bound checkType] isRequired: [Function: bound checkType] },
bool: { [Function: bound checkType] isRequired: [Function: bound checkType] },
func: { [Function: bound checkType] isRequired: [Function: bound checkType] },
number: { [Function: bound checkType] isRequired: [Function: bound checkType] },
object: { [Function: bound checkType] isRequired: [Function: bound checkType] },
string: { [Function: bound checkType] isRequired: [Function: bound checkType] },
symbol: { [Function: bound checkType] isRequired: [Function: bound checkType] },
any: { [Function: bound checkType] isRequired: [Function: bound checkType] },
arrayOf: [Function: createArrayOfTypeChecker],
element: { [Function: bound checkType] isRequired: [Function: bound checkType] },
instanceOf: [Function: createInstanceTypeChecker],
node: { [Function: bound checkType] isRequired: [Function: bound checkType] },
objectOf: [Function: createObjectOfTypeChecker],
oneOf: [Function: createEnumTypeChecker],
oneOfType: [Function: createUnionTypeChecker],
shape: [Function: createShapeTypeChecker] }
```

Start at the proptypes package entry point and inspect how its current exports are assembled. Reproduce the two require calls shown in the issue, then verify that both the direct export and the .default property expose the same PropTypes API.

Escrito por el modelo de indexación a partir del texto del issue.