Update HISTORY and release version for 2.5.3

HISTORY.rst

@@ -3,6 +3,14 @@
 Release History
 ---------------
 
+2.5.3 (2015-02-24)
+++++++++++++++++++
+
+**Bugfixes**
+
+- Revert changes to our vendored certificate bundle. For more context see
+  (#2455, #2456, and http://bugs.python.org/issue23476)
+
 2.5.2 (2015-02-23)
 ++++++++++++++++++
 

requests/__init__.py

@@ -42,8 +42,8 @@ is at <http://python-requests.org>.
 """
 
 __title__ = 'requests'
-__version__ = '2.5.2'
-__build__ = 0x020502
+__version__ = '2.5.3'
+__build__ = 0x020503
 __author__ = 'Kenneth Reitz'
 __license__ = 'Apache 2.0'
 __copyright__ = 'Copyright 2015 Kenneth Reitz'