recover description in default.gembox

mrbgems/default.gembox

@@ -1,25 +1,64 @@
 MRuby::GemBox.new do |conf|
-  # see summary property of each mrbgem for detail
-
+  # Use standard Kernel#sprintf method
   conf.gem :core => "mruby-sprintf"
+
+  # Use standard print/puts/p
   conf.gem :core => "mruby-print"
+
+  # Use standard Math module
   conf.gem :core => "mruby-math"
+
+  # Use standard Time class
   conf.gem :core => "mruby-time"
+
+  # Use standard Struct class
   conf.gem :core => "mruby-struct"
+
+  # Use extensional Enumerable module
   conf.gem :core => "mruby-enum-ext"
+
+  # Use extensional String class
   conf.gem :core => "mruby-string-ext"
+
+  # Use extensional Numeric class
   conf.gem :core => "mruby-numeric-ext"
+
+  # Use extensional Array class
   conf.gem :core => "mruby-array-ext"
+
+  # Use extensional Hash class
   conf.gem :core => "mruby-hash-ext"
+
+  # Use extensional Range class
   conf.gem :core => "mruby-range-ext"
+
+  # Use extensional Proc class
   conf.gem :core => "mruby-proc-ext"
+
+  # Use extensional Symbol class
   conf.gem :core => "mruby-symbol-ext"
+
+  # Use Random class
   conf.gem :core => "mruby-random"
+
+  # Use extensional Object class
   conf.gem :core => "mruby-object-ext"
+
+  # Use ObjectSpace class
   conf.gem :core => "mruby-objectspace"
+
+  # Use Fiber class
   conf.gem :core => "mruby-fiber"
+
+  # Use Enumerator class (require mruby-fiber)
   conf.gem :core => "mruby-enumerator"
+
+  # Use extended toplevel object (main) methods
   conf.gem :core => "mruby-toplevel-ext"
+
+  # Generate mirb command
   conf.gem :core => "mruby-bin-mirb"
+
+  # Generate mruby command
   conf.gem :core => "mruby-bin-mruby"
 end