Added a bit of minor documentation

lib/apex/encoder/aprs_kiss.rb

@@ -3,6 +3,11 @@ require 'apex/frame'
 module Apex
     class AprsKiss
 
+        ##
+        # Creates a new AprsKiss encoder
+        #
+        # @param data_stream [Kiss::KissAbstract] The underlying data stream
+        #    frames are written to.
         protected
         def initialize(data_stream)
             @data_stream = data_stream