TST: add api_core and cloud core to MASTER build

Author: tswast

.travis.yml

@@ -28,6 +28,8 @@ install:
       conda install -q numpy pytz python-dateutil;
       PRE_WHEELS="https://7933911d6844c6c53a7d-47bd50c35cd79bd838daf386af554a83.ssl.cf2.rackcdn.com";
       pip install --pre --upgrade --timeout=60 -f $PRE_WHEELS pandas;
+      pip install -e 'git+https://github.com/GoogleCloudPlatform/google-cloud-python.git#egg=version_subpkg&subdirectory=api_core';
+      pip install -e 'git+https://github.com/GoogleCloudPlatform/google-cloud-python.git#egg=version_subpkg&subdirectory=core';
       pip install -e 'git+https://github.com/GoogleCloudPlatform/google-cloud-python.git#egg=version_subpkg&subdirectory=bigquery';
     else
       conda install -q pandas=$PANDAS;