Fix mapping Google Userinfo to User Object

[joshbrown]

It seems that Google's response when fetching the user info has changed.

Updated to reflect those changes. I could not find any change log on Google's side for reference.

#314 has some more info along with the specific error.

Google Returns the following for reference:

[
    "user" => [
        "id" => "",
        "email" => "",
        "verified_email" => "",
        "name" => "",
        "given_name" => "",
        "family_name" => "",
        "link" => "",
        "picture" => "",
        "locale" => ""
    ]
]

[rjvandoesburg]

You could do Arr::get($user, 'name', Arr::get($user, 'displayName')); so the old implementation won't break.

[driesvints]

Looks like the fix from https://github.com/laravel/socialite/pull/283/files got reverted during a merge. Thanks for sending this in.

@rjvandoesburg don't think that's necessary as they key isn't present anymore.