Remove now-useless array of classes from Aggregator.

This was used to keep an array of classes in their original order, but
now that the tests use the resulting Hash instead, it's no more needed.

lib/jsduck/aggregator.rb

@@ -9,7 +9,6 @@ module JsDuck
   # class.
   class Aggregator
     def initialize
-      @documentation = []
       @classes = {}
       @alt_names = {}
       @orphans = []
@@ -63,7 +62,6 @@ module JsDuck
         @current_class = old_cls
       else
         @current_class = cls
-        @documentation << cls
         @classes[cls[:name]] = cls
 
         # Register all alternate names of class for lookup too
@@ -78,7 +76,6 @@ module JsDuck
             # it by merging the class with alt-name into this class.
             if @classes[altname]
               merge_classes(cls, @classes[altname])
-              @documentation.delete(@classes[altname])
               @classes.delete(altname)
               warn_alt_name(cls)
             end