Be more permissive about GAE SDK versions.
Be more permissive about GAE SDK versions.

Previously, we always tried to grab the *most* recent SDK version for building
docs; this change loosens this, to grab the most-recent-and-readable version.

clancychilds/oauth2client,googleapis/oauth2client,jonparrott/oauth2client,googleapis/oauth2client,google/oauth2client,clancychilds/oauth2client,google/oauth2client,jonparrott/oauth2client