function removeTab() {
                // chrome.tabs.getCurrent(function(tab) {
                //     chrome.tabs.remove(tab.id);
                // });
            }
Finishes the oauth2 process by exchanging the given authorization code for an
authorization token. The authroiztion token is saved to the browsers local storage.
If the redirect page does not return an authorization code or an error occures when 
exchanging the authorization code for an authorization token then the oauth2 process dies
and the authorization tab is closed.

@param url The url of the redirect page specified in the authorization request.