Add `mruby-io` and `mruby-pack` to `default.gembox`
MRuby::GemBox.new do |conf|
+ # Use standard IO/File class
+ conf.gem :core => "mruby-io"
+
+ # Use standard Array#pack, String#unpack methods
+ conf.gem :core => "mruby-pack"
+
# Use standard Kernel#sprintf method
conf.gem :core => "mruby-sprintf"
