added table of contents

Author: joelgrus

README.md

@@ -19,8 +19,30 @@ Or can be run from the command line to get a demo of what it does (and to execut
 python recommender_systems.py
 ```  
 
-== Table of Contents
+## Table of Contents
 
 1. Introduction
 2. A Crash Course in Python
 3. [Visualizing Data](https://github.com/joelgrus/data-science-from-scratch/blob/master/visualizing_data.py)
+4. [Linear Algebra](https://github.com/joelgrus/data-science-from-scratch/blob/master/linear_algebra.py)
+5. [Statistics](https://github.com/joelgrus/data-science-from-scratch/blob/master/statistics.py)
+6. [Probability](https://github.com/joelgrus/data-science-from-scratch/blob/master/probability.py)
+7. [Hypothesis and Inference](https://github.com/joelgrus/data-science-from-scratch/blob/master/hypothesis_and_inference.py)
+8. [Gradient Descent](https://github.com/joelgrus/data-science-from-scratch/blob/master/gradient_descent.py)
+9. [Getting Data](https://github.com/joelgrus/data-science-from-scratch/blob/master/getting_data.py)
+10. [Working With Data](https://github.com/joelgrus/data-science-from-scratch/blob/master/working_with_data.py)
+11. [Machine Learning](https://github.com/joelgrus/data-science-from-scratch/blob/master/machine_learning.py)
+12. [k-Nearest Neighbors](https://github.com/joelgrus/data-science-from-scratch/blob/master/nearest_neighbors.py)
+13. [Naive Bayes](https://github.com/joelgrus/data-science-from-scratch/blob/master/naive_bayes.py)
+14. [Simple Linear Regression](https://github.com/joelgrus/data-science-from-scratch/blob/master/simple_linear_regression.py)
+15. [Multiple Regression](https://github.com/joelgrus/data-science-from-scratch/blob/master/multiple_regression.py)
+16. [Logistic Regression](https://github.com/joelgrus/data-science-from-scratch/blob/master/logistic_regression.py)
+17. [Decision Trees](https://github.com/joelgrus/data-science-from-scratch/blob/master/decision_trees.py)
+18. [Neural Networks](https://github.com/joelgrus/data-science-from-scratch/blob/master/neural_networks.py)
+19. [Clustering](https://github.com/joelgrus/data-science-from-scratch/blob/master/clustering.py)
+20. [Natural Language Processing](https://github.com/joelgrus/data-science-from-scratch/blob/master/natural_language_processing.py)
+21. [Network Analysis](https://github.com/joelgrus/data-science-from-scratch/blob/master/network_analysis.py)
+22. [Recommender Systems](https://github.com/joelgrus/data-science-from-scratch/blob/master/recommender_systems.py)
+23. [Databases and SQL](https://github.com/joelgrus/data-science-from-scratch/blob/master/databases.py)
+24. [MapReduce](https://github.com/joelgrus/data-science-from-scratch/blob/master/mapreduce.py)
+25. Go Forth And Do Data Science