getAuthUrl does not return a promise, and causes Typescript compilation errors

[jlengrand]

See https://github.com/esteban-uo/picasa/blob/master/src/picasa.js#L129

getAuthUrl directly returns a String, but the doc mentions a Promise.

Using the code as follows :

app.get('/login', (req, res) => {
    const authURL = picasa.getAuthURL(googleConfig);
    res.redirect(authURL);
});

raises the following Typescript compilation error:

scripts/loginAndGetGoogleToken.ts:21:18 - error TS2345: Argument of type 'Promise<any>' is not assignable to parameter of type 'string'.

21     res.redirect(authURL);
                    ~~~~~~~

Because microsoft/TypeScript#19139 is still open, there is no way to fix this without changing the documentation.

The doc for this method should be changed, and mention that it returns a String instead.

[jlengrand]

Alright, see #28 for super minor fix.

Since it is my 2nd contribution, I added myself as a contributor. Let me know if that is an issue :).

Cheers!