Correct onScroll throttling

[zzorba]

Problem I observed is detailed here: #466

This PR corrects the logic in two ways:

1. Changes the throttle to compare numbers in correct direction, before the if condition was always false.
2. Start utilizing the updateTimeInterval prop which was previously being ignored throughout the code.

Wasn't totally sure about number 2, but my read was this was the logical place to control that logic.