bump version to 0.13 and set release date

CHANGES.rst

 Release Notes
 =============
 
-Version 0.13dev
----------------
+Version 0.13 (release date: 2016-03-07)
+---------------------------------------
 
 Main features:
 
@@ -27,6 +27,7 @@ API relevant changes:
 
 Other changes:
 
+* Added alignment evaluation (#12)
 * Added continous integration testing (#16)
 * Added `-o` option to both `single`/`batch` processing mode to not overwrite
   files accidentially in `single` mode (#18)

setup.py

@@ -14,7 +14,7 @@ import glob
 import numpy as np
 
 # define version
-version = '0.13.dev'
+version = '0.13'
 
 # define which extensions need to be compiled
 extensions = [Extension('madmom.ml.rnn',