Fixed tracks not being delayed

Every track from the second track onwards all started together at the same
point. This was due to delay in overlay not being offset on each loop
iteration. The delay is now calculated with the current loop number so
with each loop iteration the delay is increased.
A little more pythonic

Replacing '!=' with 'is not' to conform with the zen of python
Merge pull request #1 from MatthewMiele/development

Fixed overlays not being delayed and improving some readability