Make ToastManager.updateToastsPositions protected

[czyzby]

#374

[bploeckelman]

@czyzby I was just poking at this to make my own merge request, but you beat me to it. I think the member variables touched in updateToastsPositions() need to be set protected also. Maybe just make all members protected to cover anything an end-user would want to do?

[czyzby]

@bploeckelman I can close this PR and let you submit another one. Thanks.

(As a side note, this should also speed up the merging process, as we won't have to wait for kotcrab's review, I think.)

[bploeckelman]

Sounds good, working on it. I'll probably add support for top and bottom centering while I'm at it. I'll update TestToasts to validate those changes too. Thanks!