Switched to Simplecov.track_files to know about files that contain on…

…ly untested code

http://www.rubydoc.info/gems/simplecov/SimpleCov/Configuration#track_files-instance_method

Previously we implemented this ourselves by loading all
files but that produced false negatives for code that called
a method without requiring its file.

test/test_helper.rb

@@ -23,9 +23,9 @@
     add_filter "/test/"
   end
 
-  # for coverage we need to load all ruby files
   src_location = File.expand_path("../../src", __FILE__)
-  Dir["#{src_location}/{module,lib}/**/*.rb"].each { |f| require_relative f }
+  # track all ruby files under src
+  SimpleCov.track_files("#{src_location}/**/*.rb")
 
   # use coveralls for on-line code coverage reporting at Travis CI
   if ENV["TRAVIS"]