Update formatter in `proxy`

[przepompownia]

trafficstars

[dantleech]

Not even sure what this does... does it make sense to simply delete it?

[przepompownia]

The formatter is used to prepare two full request messages (stdin of example/server/minimal.php in the example from the start of tutorial), i.e.

echo '{"id":1,"method":"foobar","params":[]}' | ./bin/proxy request | php example/server/minimal.php