Enable code coverage testing

Author: DavidS

.sync.yml

@@ -4,3 +4,6 @@
 
 spec/spec_helper.rb:
   mock_with: ':rspec'
+
+.travis.yml:
+  simplecov: true

.travis.yml

@@ -9,7 +9,7 @@ before_install:
   - gem --version
   - bundle -v
 script:
-  - 'bundle exec rake $CHECK'
+  - 'SIMPLECOV=yes bundle exec rake $CHECK'
 bundler_args: --without system_tests
 rvm:
   - 2.5.3