Added tests.

Rakefile

@@ -1,2 +1,11 @@
 #!/usr/bin/env rake
 require "bundler/gem_tasks"
+require "rake/testtask"
+
+desc 'Run tests'
+Rake::TestTask.new(:test) do |t|
+  t.libs << 'lib'
+  t.libs << 'test'
+  t.pattern = 'test/**/*_test.rb'
+  t.verbose = true
+end