Fixes #476: Correctly handle URI which contains hostname

[jeroenvervaeke]

See detailed explanation in issue #476.

Description

This code fixes #476.

The code is now correctly handling URLs like http://example.com/favicon.ico.

Previously, because Uri::builder() .path_and_query(p) was used uri.host() would be none and path_and_query would be /http://example.com/favicon.ico.

This PR fixes that issue.
After my fix the host is now example.com and the path_and_query are /favicon.ico.

I've added the \\ normalization to fix the test_single_header and test_multiple_header unit tests.