raindrops 0.6.0 - polishing up the last release

Following up the huge 0.5.0 release, 0.6.0 makes
some minor improvements:

* minor UI/UX improvements for Watcher Rack app
* set close-on-exec by default for inet_diag sockets
* inet_diag build fixes for newer GNU libc6
* --with-atomic_ops-dir= build option added