goToOffset + Keyboard direction

[jgi-comspace]

Hi!
This PR contains two small changes/fixes:

1. The offset for "scrollThere" in .goTo() was hard coded to -100, which isn't always useful. The option goToOffset was added and documented in the readme to address this. The default value is still -100 to ensure backwards compatibility.
2. When using the Keyboard navigation, no directions were handed over to "goTo()" – this could be easily fixed, since the direction is known at that point.

cheers,
John Gibbon