Fixes positioning issue #118 (add horizontalAdjustment prop)

[topherPedersen]

This pull requests adds a new prop, horizontalAdjustment, similar to the existing topAdjustment prop, which allows horizontal adjustment of the highlighted child view should the library get the alignment wrong. I ran into the same issue described in Issue #118 yesterday, a horizontal alignment problem, and created this new prop to solve this issue in my organization's app.

[doug-sheridan]

@jasongaare , I think this is a good solution to Issue #118 and should be accepted into this library 👍

[mehakenlume]

when is it going to be merged, please so it as soon as possible.

[jasongaare]

Seems reasonable!

[sayo96]

@jasongaare This still doesn't solve the problem. All I wanted was the tooltip to be position above the element it wraps but tooltip appears a bit towards the left instead.