Removed text descrbing unused Preface.

table_of_contents.ipynb

@@ -21,7 +21,6 @@
       "[**Introduction**](http://nbviewer.ipython.org/urls/raw.github.com/rlabbe/Kalman-and-Bayesian-Filters-in-Python/master/Introduction.ipynb)\n",
       " \n",
       "Introduction to the Kalman filter. Explanation of the idea behind this book.\n",
-      "Yes, it is more or less the preface restated. will edit and delete one or the other.\n",
       "\n",
       "\n",
       "[**Chapter 1: The g-h Filter**](http://nbviewer.ipython.org/urls/raw.github.com/rlabbe/Kalman-and-Bayesian-Filters-in-Python/master/Chapter01_gh_filter/g-h_filter.ipynb)\n",