Deprecate run_tests.sh

run_tests.sh does not run the unit tests or pep8 checks as Jenkins
does, leading to commits that fail Jenkins tests. This patch replaces
its functionality with instructions for installing and running tox.

Change-Id: Ie6b13b59726ed0e7483eb91ff4095d79f058a360
Closes-Bug: #1326055
Merge "Deprecate run_tests.sh"