Fixing typos

Hello Christian,

I enjoyed reading your book and would like to contribute to it. Perhaps, I'll start by adding a section on analytics functions and windows (e.g. MAX(column) OVER (PARTITION BY idColumn)).

As a warm up, I fixed some typos to get things started. A couple of observations:

* You should probably add a section about contributors. Almost all open-source projects have this and whenever someone new makes a change, they add their names to the list as part of the commit.
* There's no readme section for contributors. I'd be happy to add this once I figure out how everything is setup, which brings me to the next point:
* How are the pdf, and html generated? I assume you use Marked to generate them from the .md files. Is that correct? This may be overkill, but if we could setup some continous deployment so that whenever a change to the .md file is made, the other files are generated automatically, that would be great. Failing that, may be we can add some script in the repository to do that?

Thanks,
-Ameen