Merge pull request #993 from esparta/master

[en] Adding Python for Econometrics

free-programming-books.md

@@ -1356,6 +1356,7 @@ See also [TeX](#tex)
 * [Python 2.7 quick reference](http://infohost.nmt.edu/tcc/help/pubs/python/web/) - New Mexico Tech
 * [Python Bibliotheca](http://openbookproject.net/pybiblio/)
 * [Python Cookbook](http://chimera.labs.oreilly.com/books/1230000000393/index.html) - David Beazley
+* [Python for Econometrics](http://www.kevinsheppard.com/images/0/09/Python_introduction.pdf) - Kevin Sheppard
 * [Python for Fun](http://www.openbookproject.net/py4fun/)
 * [Python for Informatics: Exploring Information](http://www.pythonlearn.com/book.php)
 * [Python for you and me](http://pymbook.readthedocs.org/en/latest/)