Feature: Forward compatibility with react/http-client v0.5 (#72 and #73 by @clue)

Older HttpClient versions are still supported, but the new version is now preferred. Advanced usage with custom connectors now recommends setting up the React\HttpClient\Client instance explicitly.

Accordingly, the Sender::createFromLoopDns() and Sender::createFromLoopConnectors() have been marked as deprecated and will be removed in future versions.