Add Chapter 8 to README

Author: jvns

README.md

@@ -33,6 +33,7 @@ Table of Contents
 * [Chapter 5: Combining dataframes and scraping Canadian weather data](http://nbviewer.ipython.org/github/jvns/pandas-cookbook/blob/master/cookbook/Chapter%205%20-%20Combining%20dataframes%20and%20scraping%20Canadian%20weather%20data.ipynb)
 * [Chapter 6: String operations! Which month was the snowiest?](http://nbviewer.ipython.org/github/jvns/pandas-cookbook/blob/master/cookbook/Chapter%206%20-%20String%20operations%21%20Which%20month%20was%20the%20snowiest%3F.ipynb)
 * [Chapter 7: Cleaning up messy data](http://nbviewer.ipython.org/github/jvns/pandas-cookbook/blob/master/cookbook/Chapter%207%20-%20Cleaning%20up%20messy%20data.ipynb)
+* [Chapter 8: Parsing Unix timestamps](http://nbviewer.ipython.org/github/jvns/pandas-cookbook/blob/master/cookbook/Chapter%208%20-%20How%20to%20deal%20with%20timestamps.ipynb)