Make code that uses `vmath.lerp` frametime-independent.

[aglitchman]

Describe the bug Current, the code has lots of vmath.lerp calls. It assumes that the user has the constant 60 FPS.

To Reproduce Run the examples on higher or lower framerates.

Expected behavior The code should be deltatime-independent.

Additional context (optional) Using lerp with delta-time

[subsoap]

Use socket.gettime() differences between frames to calculate accurate dt.