Update development dependencies to latest versions

Updated to the current latest version.

Author: ydah

Gemfile

@@ -2,8 +2,9 @@ source "https://rubygems.org"
 
 group :development do
   gem "racc"
-  gem "rake", "13.0.6"
-  gem "rake-compiler", "1.2.3"
-  gem "test-unit", "3.6.1"
-  gem "test-unit-ruby-core", "1.0.5"
+  gem "rake", "13.3.0"
+  gem "rake-compiler", "1.3.0"
+  gem "rdoc", "6.5.11"
+  gem "test-unit", "3.6.8"
+  gem "test-unit-ruby-core", "1.0.6"
 end