ci(travis): filtering commits without code change

.travis.yml

@@ -14,6 +14,16 @@ node_js:
  - "6"
 
 before_install:
+ # https://github.com/scikit-learn/scikit-learn/issues/10927
+ - |
+ set -e
+ # fail loudly when force-pushed
+ MODIFIED_FILES=$(git diff --name-only $TRAVIS_COMMIT_RANGE)
+ # waiting for native solution https://github.com/travis-ci/travis-ci/issues/6301
+ if ! echo ${MODIFIED_FILES} | grep -qvE '(\.md$)|(^docs)/'; then
+ echo "Only docs were updated, stopping build process."
+ exit
+ fi
  - dpkg --compare-versions `npm -v` ge 5.8 || npm i -g npm@latest
 
 script: