## Why?
Typescript requires assign of `navigation` on Component that is created with `withNavigation` HOC. But it comes with that function so it shouldn't require that property.
## Example
```typescript
//
// on the current version, this will give an error.
// with this PR, it will work.
//
interface IHelloProps extends Partial<NavigationInjectedProps> {
hello: boolean;
}
const HelloBox: SFC<IHelloProps> = ({ navigation, hello }) => (
<View>
<TouchableHighlightCustom onPress={() => navigation.navigate('TEST', { hello })}>
<Text>Hello</Text>
</TouchableHighlightCustom>
</View>;
);
export default withNavigation(HelloBox);
```
----
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* correct type for withNavigation onRef, add generic to access class methods
* tests for withNavigation class correctness
* tabbing
* remove generic, add explicit type suggestion
* Adding a failing test for getParam
This demonstrates that typing of `navigation.getParam` works when a parameter type is provided.
This fails with the following error:
```
ERROR: 559:54 expect TypeScript@next compile error:
Argument of type '"title"' is not assignable to parameter of type '"unknown"'.
```
* Making test pass
