minor typos and reformatting

README.md

@@ -1,7 +1,16 @@
 Welcome to CS109: Data Science
 =======
 
+## Assignments
 
-* [Setting up Python](https://github.com/cs109/content/wiki/Installing-Python)
 * [Homework 0](http://nbviewer.ipython.org/urls/raw.github.com/cs109/content/master/HW0.ipynb): Hello, world
 * [Homework 1](http://nbviewer.ipython.org/urls/raw.github.com/cs109/content/master/HW1.ipynb): Which of two things is larger?
+
+## Lecture Supplements
+
+* [A gallery of statistical graphs with matplotlib](http://nbviewer.ipython.org/urls/raw.github.com/cs109/content/master/lec_03_statistical_graphs.ipynb) (see also the version with [default matplotlib styles](http://nbviewer.ipython.org/urls/raw.github.com/cs109/content/master/lec_03_statistical_graphs_mpl_default.ipynb)
+* [A rubric for data wrangling and exploratory data analysis](http://nbviewer.ipython.org/urls/raw.github.com/cs109/content/master/lec_04_wrangling.ipynb)
+
+## Other Resources
+
+* [Setting up Python](https://github.com/cs109/content/wiki/Installing-Python)