Add release notes for 1.5.3

Conflicts:
	CHANGELOG.txt
	docs/releases/index.rst

CHANGELOG.txt

@@ -34,6 +34,12 @@ Changelog
  * Fix: Fixed styling glitch on bi-colour icon + text buttons in Chrome (Janneke Janssen)
 
 
+1.5.3 (18.07.2016)
+~~~~~~~~~~~~~~~~~~
+
+ * Fix: Pin html5lib to version 0.999999 to prevent breakage caused by internal API changes (Liam Brenner)
+
+
 1.5.2 (08.06.2016)
 ~~~~~~~~~~~~~~~~~~
 

docs/releases/1.5.3.rst

@@ -0,0 +1,16 @@
+===========================
+Wagtail 1.5.3 release notes
+===========================
+
+.. contents::
+    :local:
+    :depth: 1
+
+
+What's changed
+==============
+
+Bug fixes
+~~~~~~~~~
+
+ * Pin html5lib to version 0.999999 to prevent breakage caused by internal API changes (Liam Brenner)

docs/releases/index.rst

@@ -5,6 +5,7 @@ Release notes
    :maxdepth: 1
 
    1.6
+   1.5.3
    1.5.2
    1.5.1
    1.5