Add Python 2.4

Author: Graham Higgins

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 envlist = 
-    py25,py26,py27,py32,pypy,jython,cover
+    py24,py25,py26,py27,py32,pypy,jython,cover
 
 [testenv]
 commands = 
@@ -11,6 +11,14 @@ deps =
     nose
     isodate
 
+[testenv:py24]
+basepython =
+    python2.4
+commands = 
+    python setup.py clean --all
+    python setup.py build
+    nosetests --where=./ --with-xunit
+
 [testenv:py25]
 basepython =
     python2.5