Redirect bug

Hello again, sorry for spam.

I have noticed the redirection system is somewhat faulty. When redirecting, it does not call url.resolve, so redirects will entirely malfunction if you got a relative path.

To solve this, navigate to the line within index.js, containing the comment `// Follow 3xx redirects` and update it to
`opts.url = url.resolve(url.format(opts), res.headers.location); // Follow 3xx redirects`

Again, sorry for spamming the issues section.

Regards.