Require wrapper class file only if it is specified

With my code I ran into situation when I rely fully on class loading subsystem and don't know the absolute path for wrapper class PHP file. The change I propose escapes the necessity to require exact file location. The autoload facility will deal with finding the file.

Another change is just adding to Yandex provider ability to set redirect_uri, since Yandex Oauth requires it to be exact. Google provider does the same, I just have copied the code from it.