* reverseproxy: Mask the WS close message when we're the client
* weakrand
* Bump golangci-lint version so path ignores work on Windows
* gofmt
* ugh, gofmt everything, I guess
* push: Implement HTTP/2 server push (close#3551)
* push: Abstract header ops by embedding into new struct type
This will allow us to add more fields to customize headers in
push-specific ways in the future.
* push: Ensure Link resources are pushed before response is written
* Change header name from X-Caddy-Push to Caddy-Push
