Trigger Binder builds on both GKE and OVH clusters (#493)

* Trigger Binder builds on both GKE and OVH clusters

Author: matthewfeickert

.travis.yml

@@ -94,8 +94,9 @@ jobs:
     before_install: skip
     install: skip
     script:
-      # Use Binder build API to trigger repo2docker to build image
-      - bash binder/trigger_binder.sh https://mybinder.org/build/gh/diana-hep/pyhf/"${TRAVIS_BRANCH}"
+      # Use Binder build API to trigger repo2docker to build image on GKE and OVH Binder Federation clusters
+      - bash binder/trigger_binder.sh https://gke.mybinder.org/build/gh/diana-hep/pyhf/"${TRAVIS_BRANCH}"
+      - bash binder/trigger_binder.sh https://ovh.mybinder.org/build/gh/diana-hep/pyhf/"${TRAVIS_BRANCH}"
     after_success: skip
   - stage: deploy
     # Tests deployment to PyPI for all commits to master