Added CHANGELOG additions for @id, @type maps, along with indexed graphs.

Author: gkellogg

CHANGELOG.md

@@ -13,6 +13,10 @@
 - Set processingMode from options or first encountered context.
 - Use array representation of @container in processing.
 
+### Added
+- Index graph containers using `@id` and `@index`, with `@set` variations.
+- Index node objects using `@id` and `@type`, with `@set` variations.
+
 ## 0.5.15 - 2017-10-16
 
 ### Changed