Update README.md

Author: ujjwalkarn

README.md

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 - [10 minutes to Pandas](http://pandas.pydata.org/pandas-docs/stable/10min.html)
 - [Useful Pandas Snippets](http://www.swegler.com/becky/blog/2014/08/06/useful-pandas-snippets/)
 - [Timeseries analysis using Pandas](http://nbviewer.jupyter.org/github/twiecki/financial-analysis-python-tutorial/blob/master/1.%20Pandas%20Basics.ipynb)
+- [Pandas Exercises - Practice your Pandas skills](https://github.com/guipsamora/pandas_exercises)
 - [Grouping in Pandas](http://blog.yhat.com/posts/grouping-pandas.html)
 - [**“Large data” work flows using pandas**](http://stackoverflow.com/questions/14262433/large-data-work-flows-using-pandas)
 - [Easier data analysis with pandas (video series)](http://www.dataschool.io/easier-data-analysis-with-pandas/)