(I'm also from Twilio) We historically have not done version bumps for minor improvements to the API that do not break existing applications. 2010-04-01 has be

(I'm also from Twilio) We historically have not done version bumps for minor improvements to the API that do not break existing applications. 2010-04-01 has been updated a couple times since it was first released with new features (like subaccounts, applications and short codes) but all of those were additive there was no reason to change the version.