feat: Implements a more true to game code intceil calculation

[theRTC204]

This replaces all instances of Math.floor() and Math.ceil() with a calculation that more closely matches the C++ implementation in game. In the extracted code, the all values are passed through a function intceil() which is implemented as...

int intceil(float val)
{
    return (int)(val + 0.99999f);
}

In C++ the behaviour of casting to an int results in a truncated value, not a rounded value. As such, there are situations where using JavaScript's Math.floor() or Math.ceil() can result in a value that is off by one. By using Math.trunc(), we can more closely represent the C++ behaviour.

I know we already have reports of calculation issues, and there is a feeling that having a wider net of possible values can reduce the number of failed predictions, but I personally feel the wider net makes it more difficult to diagnose potential problems in this app's calculations. I feel it would be best to represent the in-game calculation as closely as possible.

Open to discussion of course!

Closes #47

[mikebryant]

Sure, works for me