v0.7

Merge pull request #100 from bshaffer/fixes-gce-last-received-token

fixes GCE::getLastReceivedToken

v0.6

Merge pull request #93 from bshaffer/misc-fixes

misc fixes - usability and doc fix

v0.5

Adds support for Guzzle 6

v0.4

Merge pull request #80 from google/support-both-firebase-jwt-versions

supports both firebase jwt versions

v0.3

Merge pull request #77 from google/add-set-subject-on-service-account…

v0.2-alpha: Merge pull request #75 from google/add-appidentity-subscriber

adds AppIdentityCredentials

v0.1-alpha

Merge pull request #64 from bshaffer/pushes-http-client-to-authtoken-…