[proxy] Add tls support

Caveats:
* TLS files must be present on the target server (and readable)
* TLS file paths cannot contain spaces
* TLS file paths must be absolute (i.e. cannot be relative)
* Bash argument parsing is terrible

Makefile

@@ -111,6 +111,7 @@ publish: $(PUBLISH)
 clean:
 	-$(SUDO) docker rmi $(IMAGES)
 	rm -f $(EXES) $(EXPORTS)
+	rm -f test/tls/*.pem
 
 build:
 	$(SUDO) go clean -i net