Hometown can be string

Hometown in facebook can be entered just as a string. It's lead to exception. You can check it by executing following code: `FbGraph::User.fetch 'alexeyushka111'`. I've provided pull request for fb mock with new private json file which can help to test it. After it'll be merged I'll add here spec for this case.

What do you think about this fix? Maybe there is a better way?