Added release date for 1.9.1/1.8.8 releases.

docs/releases/1.8.8.txt

@@ -2,7 +2,7 @@
 Django 1.8.8 release notes
 ==========================
 
-*Under development*
+*January 2, 2016*
 
 Django 1.8.8 fixes several bugs in 1.8.7.
 

docs/releases/1.9.1.txt

@@ -2,7 +2,7 @@
 Django 1.9.1 release notes
 ==========================
 
-*Under development*
+*January 2, 2016*
 
 Django 1.9.1 fixes several bugs in 1.9.