Typos in Lessons 7,8&9

Dear Lorena,
I chose to blitz through the lessons of AeroPython to understand how IPython Notebooks work and in the process learned Aerodynamics and a little bit of Python.
Earlier I have only watched the videos of your CFD course on iTunes. This concept of Notebooks really gives much temptation to code.
However, it is not my place to go about picking typos, I did find a few of them in the lessons. I took the liberty to fork your project and correct them myself.
I hope I haven't broken anything in the process.
Thanks,
Awaiz.