Mark 1.13 as no longer in development

Conflicts:
	CHANGELOG.txt

CHANGELOG.txt

@@ -9,7 +9,7 @@ Changelog
  * Fix: Do not remove stopwords when generating slugs from non-ASCII titles, to avoid issues with incorrect word boundaries (Sævar Öfjörð Magnússon)
 
 
-1.13 (xx.xx.xxxx) - IN DEVELOPMENT
+1.13 (16.10.2017)
 ~~~~~~~~~~~~~~~~~
 
  * Front-end cache invalidator now supports purging URLs as a batch (Karl Hobley)

docs/releases/1.13.rst

@@ -1,6 +1,6 @@
-===========================================
-Wagtail 1.13 release notes - IN DEVELOPMENT
-===========================================
+==========================
+Wagtail 1.13 release notes
+==========================
 
 .. contents::
     :local:
@@ -44,6 +44,3 @@ Bug fixes
  * Removed deprecated ``SessionAuthenticationMiddleware`` from project template (Samir Shah)
  * Custom display page titles defined with ``get_admin_display_title`` are now shown in search results (Ben Sturmfels, Matt Westcott)
  * Custom PageManagers now return the correct PageQuerySet subclass (Matt Westcott)
-
-Upgrade considerations
-======================