Add db-ping.dev wrapper script

This makes it easy to run the in-development version of db-ping from its
source directory or any other (e.g.
/path/to/local-repos/db-ping/db-ping.dev or ./db-ping.dev).

See discussion at #2 (comment)

Author: dlenski

db-ping.dev

@@ -0,0 +1,6 @@
+#!/bin/sh
+
+# This wrapper script runs the in-development
+# version of db-ping from this directory.
+
+PYTHONPATH="$(dirname $0):$PYTHONPATH" python3 -m db_ping "$@"