HTTP version usage is inconsistent upon request/response modification

[hacker1024]

When modifying HTTP messages, the HTTP version field is not taken into consideration, and always set to HTTP/1.1. This causes issues, as the headers set by the client may vary based on the protocol it thinks it's using.

[hacker1024]

As of cd4dee4, the HTTP version is properly accounted for, which is visible in the web UI. The issue still persists at some level though, and HTTP/2.0 requests remain broken.

[hacker1024]

As a workaround, mitmproxy can be launched with --set 'http2=false' to disable HTTP 2 entirely.