AD-HOC fix (Layout): Prevent the paper-card element overlapping
AD-HOC fix (Layout): Prevent the paper-card element overlapping

Currently there is a problem in which the `app-card` element overlaps
two other elements:

- app-drawer
- app-layout

when those elements are brought to the "front" of the view. This commit
modifies those elements `z-index` property such that they're layered
over-top of the `paper-card` element as intended.

andrewhowdencom/www.andrewhowden.com