Update .travis.yml (#80)

* Update .travis.yml

* Update .travis.yml

Co-Authored-By: Adam Babik <adam@status.im>

.travis.yml

@@ -5,6 +5,18 @@ language: go
 
 install: true
 
+branches:
+  only:
+    - master
+
+before_install:
+  - |
+      if ! git diff --name-only $TRAVIS_COMMIT_RANGE | grep -qvE '(.md)|(.html)|^(LICENSE)|^(docs)'
+      then
+        echo "Only docs were updated, not running the CI."
+        exit 0
+      fi
+
 env:
 - GO111MODULE=on