Merge pull request #680 from estroz/md-skip-ci

.travisl.yml: skip CI on change to docs or untestable project files

Author: estroz

.travis.yml

@@ -8,6 +8,13 @@ services:
 go:
 - 1.10.3
 
+before_install:
+  - |
+      if ! git diff --name-only $TRAVIS_COMMIT_RANGE | grep -qvE '(\.md)|(\.MD)|(\.png)|(\.pdf)|^(doc/)|^(MAINTAINERS)|^(LICENSE)'; then
+        echo "Only doc files were updated, not running the CI."
+        exit
+      fi
+
 jobs:
   include:
     - before_script: hack/ci/setup-openshift.sh