.travis.yml in percy-common-2.0.0 vs .travis.yml in percy-common-2.1.0

@@ -3,9 +3,10 @@
 cache: bundler
 rvm:
   - 2.4
   - ruby-head
 before_install:
+  - gem update --system
   - gem update bundler
 script:
   - bundle exec rubocop -D
   - bundle exec rspec