Ignore non-final responses.

[ioquatix]

While informational responses are not particularly popular, we should at least ignore them. Later, we may expose them to the user.

Types of Changes

• Bug fix.

Contribution

• [ ] I added tests for my changes.
• [ ] I tested my changes locally.
• [x] I agree to the Developer's Certificate of Origin 1.1.

[ioquatix]

The HTTP/2 headers processing could probably be better, but it seems to pass all tests.