Adding client_id only requests and path query parameter support

When an empty `oauth_token` is provided the `client_id` will be used for the request. When the requested path contains a `?` the query string will be appended with an `&`.

Example use case:
*As a user, I would like to search Soundcloud without logging in.*
This is satisfied by making a request to `/track?q=$search_term&client_id=$client_id`.