App Engine SDK version 1.8.0.
Merge branch 'master' into sdk-1.8.0
Bump version.
Merge branch 'master' into sdk-1.8.0

Conflicts:
	setup.py
update DOWNLOAD_URL to storage.googleapis.com
Merge branch 'sdk-1.8.0'

Conflicts:
	appengine.py
	setup.py