Find does not traverse ObjectPattern's TypeAnnotation

This probably has the same root cause as issue #34 , but I thought I'd flag it just in case:

`find` seems to have trouble searching through type annotations of object patterns. It can't find the identifier T, nor the `TypeAnnotation` here:

```
function f({x}: {x: T}) {}
```

But it can find both without the `ObjectPattern`:

```
function f(obj: {x: T}) {}
```

Example: http://astexplorer.net/#/tHx2YYTvvd/1