Add some more doc

lib/rubella/input/json.rb

@@ -6,23 +6,38 @@ module Rubella
     #
     #
     class JSON
-
       attr_reader :data
 
+      # Constructor
+      # This constructer can create a new Rubella::Input::JSON object, but it
+      # is supposed to be private. Please use Rubella::Input::JSON.string or
+      # Rubella::Input::JSON.file to create a new instance.
+      #
+      # @param json__string string A string, which contains the data as json
+      # @return Rubella::Input::JSON
       def initialize(json_string)
         @data = ::JSON::load(json_string)
       end
 
+      # Constructor
+      # Creates a new Rubella::Input::JSON object, from the given json.
+      #
+      # @param json_string string A string, which contains the data as json
+      # @return Rubella::Input::JSON
       def self.string(json_string)
         self.new(json_string)
       end
 
+      # Constructor
+      # Creates a new Rubella::Input::JSON object, from the given file.
+      # Only the file name is required.
+      #
+      # @param json_file string The name of the file, which json contains
+      # @return Rubella:Input::JSON
       def self.file(json_file)
         self.new File.new(json_file, 'r')
       end
 
-      # private :new
-
     end
 
   end