Adding Text to Static Analysis Chapter

I've added the beginning (intro sections) of the chapter. I'm going to add 4 more sections, one for each of three "checks" that TypeCheck can make.

There probably needs to be more "this is how this works in Julia" notes added to the early code examples.
I had to stop here: I will try to read through the rest over sometime today. At worst, I'll have the rest of my commentary finished within 24 hours.