Added startAvg(), endAvg(maxTicks) and tickAvg(maxTicks) to average timings over X ticks.

Right now, it's very difficult to read unstable timings that update every frame, so I added an average alternative.

Usage is similar to `.start()` and `.end()` except that you need to provide the number of ticks per average in `endAvg(maxTicks)`

Great work so far btw! Using it on a project atm.

Also, forgive my editor stripping extra whitespaces, but it's good practice.