docs: New "Verifying App Behavior on the Android Runtime (ART)" guide.

Contains information for developers to make sure their apps work properly
with the ART runtime.

This doc is staged to:

http://asolovay.mtv:9001/guide/practices/verifying-apps-art.html

This is intended to be a companion to the newly-expanded "Introducing ART"
doc on source.android.com (http://ag/469776), which has general information
about ART's new features.

Change-Id: I77c6e552cfedb13dee1d256fec15926fffcbbbb3