ci: install robotframework-lint and html5validator in one command

Signed-off-by: asm0dey <[email protected]>

Author: asm0dey

.travis.yml

@@ -22,8 +22,7 @@ before_script:
       mkdir -p /tmp/uploads /tmp/preview;
       cp src/main/resources/test/test.png /tmp/uploads/1.png;
       npm install -g bootlint;
-      pip install --user html5validator;
-      pip install --user robotframework-lint;
+      pip install --user html5validator robotframework-lint;
       if [ "$TRAVIS_BRANCH" = 'prod' -a "$TRAVIS_PULL_REQUEST" = 'false' ]; then
         pip install --user ansible==2.1.1.0;
       fi;