Update changelog

Author: csswizardry

CHANGELOG.md

@@ -17,3 +17,4 @@
 * **1.9**       Allow users to use a non-markup fix for `inline-block` whitespace removal
 * **2.0.0**     Tighten up use of modifier (`--`) syntax.
 * **2.1.0**     Make distinction between right-aligning and reversing grids, provide a way to do both.
+* **2.2.0**     Drop `@extend`, add default flags, add gutter and vertical alignment modifiers