**Describe the bug**
When using https://github.com/axios/axios/pull/1712 example and adding baseURL in config, baseURL seems to not be used.

**To Reproduce**

```js
const axios = require("axios");
const fakeConfig = {
  method: "post",
  url: "/user/12345",
  baseURL: "/foo"
};
console.log(axios.getUri(fakeConfig));
```

**Expected behavior**
`axios.getUri` should return `/foo/user/12345`.

If this expected behavior seems right, I can work on a fix.

**Environment:**
 - Axios Version: 0.19.0
 - OS: Linux, Windows
 - Browser Chrome but also happen on Firefox and node
test/specs/api.spec.js
it('should have factory method', function () {
    expect(typeof axios.create).toEqual('function');
  });
  it('should have Cancel, CancelToken, and isCancel properties', function () {
    expect(typeof axios.Cancel).toEqual('function');
    expect(typeof axios.CancelToken).toEqual('function');
    expect(typeof axios.isCancel).toEqual('function');
  });
  it('should have isAxiosError properties', function () {
    expect(typeof axios.isAxiosError).toEqual('function');
  });
});
describe('instance api', function () {
  var instance = axios.create();
  it('should have request methods', function () {
    expect(typeof instance.request).toEqual('function');
    expect(typeof instance.get).toEqual('function');
    expect(typeof instance.options).toEqual('function');
    expect(typeof instance.head).toEqual('function');
    expect(typeof instance.delete).toEqual('function');
    expect(typeof instance.post).toEqual('function');
    expect(typeof instance.put).toEqual('function');
    expect(typeof instance.patch).toEqual('function');
  });
  it('should have interceptors', function () {
    expect(typeof instance.interceptors.request).toEqual('object');
    expect(typeof instance.interceptors.response).toEqual('object');
  });
});