Update Rakefile to only run tests in "test/matrixeval" folder

Author: hoppergee

Rakefile

@@ -6,7 +6,7 @@ require "rake/testtask"
 Rake::TestTask.new(:test) do |t|
   t.libs << "test"
   t.libs << "lib"
-  t.test_files = FileList["test/**/*_test.rb"]
+  t.test_files = FileList["test/matrixeval/**/*_test.rb"]
 end
 
 task default: :test