Update CHANGELOGfor 1.2.1.

Author: chriskrycho

CHANGELOG.md

@@ -6,6 +6,12 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/) a
 
 ## [Unreleased]
 
+## [1.2.1] - 2018-03-14
+
+### Fixed
+
+* Blueprint now correctly adds ember-cli-typescript as a dependency, allowing TS to be merged into the regular app tree.
+
 ## [1.2.0] - 2018-03-05
 
 ### Added