Trying to save resources for Travis/CI (3.0)

See https://github.com/google/EarlGrey/pull/383/files/3b38a5dea36a88aba42a42931e77a7c5429a1837

.travis.yml

@@ -6,6 +6,12 @@ addons:
     packages:
     - dnsutils
     - jsonlint
+before_install:
+  - if ! git diff --name-only $TRAVIS_COMMIT_RANGE | grep -qvE '(.md)|(.pem)|(.pdf)|(.html)|^(LICENSE)|^(docs)|^(utils)|^(bin)|(Dockerfile)'
+    then
+      echo "no code was updated, not running the CI."
+      exit
+  fi
 install:
   - cpanm --notest Test::More
   - cpanm --notest Data::Dumper