Describe the bug
When using the request() method on an instance, the request throws an error if the instance's config has url specified, but not baseUrl.

Error indicates a missing url arg:

The "url" argument must be of type string. Received type undefined

This contradicts the documentation, which states that

Only the url is required.

and

baseURL will be prepended to url unless url is absolute.

To Reproduce
Code snippet to reproduce, ideally that will work by pasting into something like https://npm.runkit.com/axios, a hosted solution, or a repository that illustrates the issue. If your problem is not reproducible, please file under Support or Usage Question

var axios = require("axios")

// this works
axios.create({ baseURL: 'https://www.google.com/' })
    .request()
    .then(response => console.log(`response status: ${response.status}`))
    .catch(err => console.log(err));

// this errors
axios.create({ url: 'https://www.google.com/' })
    .request()
    .then(response => console.log(`response status: ${response.status}`))
    .catch(err => console.log(err));

Expected behavior
The request should use the url property if present and absolute. Alternatively, the documentation should reflect that baseUrl is required to use instance.request().

Environment:

• Axios Version: 0.19.0
• OS: Windows 10 Pro 1803
• Browser: Chrome 74.0.3729.169 64-bit