Merge a fix to the tests' simplecov setup from #58

This fixes a deprecation warning:

    simplecov_formatter_class: [DEPRECATION] ::[] is deprecated.
    Use ::new instead.

References #57.

test/helpers/start_simplecov.rb

@@ -24,7 +24,7 @@ def simplecov_formatter_class
         formatters << Console
         formatters << HTMLFormatter if html_report_requested?
       end
-      MultiFormatter[*formatters]
+      MultiFormatter.new(formatters)
     end
 
     def this_process_responsible_for_coverage_reporting?