Incorrect Tween Duration

[sam-ln]

Describe the bug
Depending on the chosen duration for a tween, the time passes faster or slower than expected, causing the tween to finish too soon or too late.

To Reproduce
Attach any tween to a GameObject with a duration different from 1.
View the tween in the "Tweens" window.
The time within the tween will pass 5x slower if a duration of 5 seconds was chosen, totalling a run time of 25 seconds.

Additional context
The behaviour is caused by this line.

unity-tweens/Runtime/TweenInstance.cs

Line 105 in c4f2322

 var timeStep = deltaTime / duration; 

I'll create a pull request with a fix shortly.