Add Kubernetes auth providers (#2147)

* Import auth providers for K8s

* Vendor updates for K8s auth providers

* Remove Azure since it is not compiling

* Update vendor to remove Azure dependencies

vendor/cloud.google.com/go/.travis.yml

@@ -0,0 +1,25 @@
+sudo: false
+language: go
+go:
+- 1.6.x
+- 1.7.x
+- 1.8.x
+- 1.9.x
+- 1.10.x
+- 1.11.x
+install:
+- go get -v cloud.google.com/go/...
+script:
+- openssl aes-256-cbc -K $encrypted_a8b3f4fc85f4_key -iv $encrypted_a8b3f4fc85f4_iv -in keys.tar.enc -out keys.tar -d
+- tar xvf keys.tar
+- GCLOUD_TESTS_GOLANG_PROJECT_ID="dulcet-port-762"
+  GCLOUD_TESTS_GOLANG_KEY="$(pwd)/dulcet-port-762-key.json"
+  GCLOUD_TESTS_GOLANG_FIRESTORE_PROJECT_ID="gcloud-golang-firestore-tests"
+  GCLOUD_TESTS_GOLANG_FIRESTORE_KEY="$(pwd)/gcloud-golang-firestore-tests-key.json"
+  GCLOUD_TESTS_GOLANG_KEYRING="projects/dulcet-port-762/locations/us/keyRings/go-integration-test"
+  GCLOUD_TESTS_GOLANG_ENABLE_REPLAY=yes
+  travis_wait ./run-tests.sh $TRAVIS_COMMIT
+env:
+  matrix:
+    # The GCLOUD_TESTS_API_KEY environment variable.
+    secure: VdldogUOoubQ60LhuHJ+g/aJoBiujkSkWEWl79Zb8cvQorcQbxISS+JsOOp4QkUOU4WwaHAm8/3pIH1QMWOR6O78DaLmDKi5Q4RpkVdCpUXy+OAfQaZIcBsispMrjxLXnqFjo9ELnrArfjoeCTzaX0QTCfwQwVmigC8rR30JBKI=