ability to use proxy handler in independent way (attach to express for example)

I want to use this proxy as express middleware/handler (mapped to some mount path). Header "x-cors-anywhere-url" added to simplify obtaining URL in this case.
Could you undo this unrelated change, then squash your commits?

E.g. after adding another commit that changes xfwd, you can use the following:

```
git rebase -i HEAD~3
```

This will open an editor and lists 3 commits. Use "pick" for the base commit and "fixup" for your changes. That will create a single commit.

Use `git push origin master -f` to forcidbly push the changes to Github. Github will automatically update the PR with the new commits.