Fill in release date for 2.1

Conflicts:
	CHANGELOG.txt

CHANGELOG.txt

@@ -8,7 +8,7 @@ Changelog
  * Added `annotate_score` support to PostgreSQL search backend (Bertrand Bordage)
 
 
-2.1 (xx.xx.xxxx) - IN DEVELOPMENT
+2.1 (22.05.2018)
 ~~~~~~~~~~~~~~~~
 
  * Add `HelpPanel` to add HTML within an edit form (Keving Chung)

docs/releases/2.1.rst

@@ -1,6 +1,6 @@
-==========================================
-Wagtail 2.1 release notes - IN DEVELOPMENT
-==========================================
+=========================
+Wagtail 2.1 release notes
+=========================
 
 .. contents::
     :local: