Smoke test now uses portable file path

Added a sanity check to ensure smoke.sh is run from the correct folder
and use a relative path to the mona image so it works on any system.

You won't believe how long I spent trying to debug why the smoke test was core dumping on my system, only to finally look inside smoketest.js and discover that it was simply failing to load a non-existent image. This should improve on that a little.

Looks like you've made one new release since your presentation at OS Bridge, I'll have to take a look.