Update URL to Timing and Profiling in IPython

Apparently the blog has been updated and the URL has changed, it is still there though.

doc/py_tutorials/py_core/py_optimization/py_optimization.markdown

@@ -163,7 +163,7 @@ Additional Resources
 -#  [Python Optimization Techniques](http://wiki.python.org/moin/PythonSpeed/PerformanceTips)
 2.  Scipy Lecture Notes - [Advanced
     Numpy](http://scipy-lectures.github.io/advanced/advanced_numpy/index.html#advanced-numpy)
-3.  [Timing and Profiling in IPython](http://pynash.org/2013/03/06/timing-and-profiling.html)
+3.  [Timing and Profiling in IPython](http://pynash.org/2013/03/06/timing-and-profiling/)
 
 Exercises
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