chore: dont run travis for docs updates

.travis.yml

@@ -3,7 +3,7 @@ dist: bionic
 sudo: true
 
 git:
-  depth: 1
+  depth: 10
 
 cache:
   - pip
@@ -70,6 +70,16 @@ matrix:
     env: TEST=easy_install
     script: sudo python $TRAVIS_BUILD_DIR/install.py --user travis --run-travis --production --verbose
 
+before_install:
+- |
+    if [ "$TRAVIS_PULL_REQUEST" != "false" ]; then
+      TRAVIS_COMMIT_RANGE="FETCH_HEAD...$TRAVIS_BRANCH"
+    fi
+    git diff --name-only $TRAVIS_COMMIT_RANGE | grep -qvE '\.md$|^docs' || {
+      echo "Only docs were updated, stopping build process."
+      exit
+    }
+
 install:
   - pip install urllib3 pyOpenSSL ndg-httpsclient pyasn1