.travis.yml in autobuild-1.18.0 vs .travis.yml in autobuild-1.18.1

@@ -1,18 +1,17 @@
 sudo: true
 language: ruby
 rvm:
-  - '2.1'
-  - '2.2'
   - '2.3'
   - '2.4'
   - '2.5'
   - 'jruby-9.1.15.0'
 matrix:
     allow_failures:
         - rvm: 'jruby-9.1.15.0'
 
 install:
+  - sudo apt-get install build-essential
   - gem install bundler
   - bundle install --path vendor/bundle
 
 script:
   - bundle exec rake