allowing camelCase method calls

As in
```
$posts = Post::findAllByCategory('music');
//..
$user = \models\User::findByEmail('user@example.com');
//..
echo $post->toJSON();
```
Why even have this `method_exists()` check block?
This won't allow for the `build` or `create` methods and this `__call` method already handles the error case if a method doesn't exist.