Initial writeup of lesson 1

Hey, @EvanSimpson and @benkahle, take a look at the lesson 1 writeup and let me know what you think.
Maybe change to something like

Welcome to week one of PyCharmers. To start, we'll be going over an introduction to Python, a general-purpose high-level programming language. For those of you familiar with MATLAB, we'll try to draw parallels between the two languages throughout our introduction.