Added a solutions file. Fixed small things in GMRES lab.

I went through the lab up until the section "Optimizing Least-Squares for GMRES". Even after that I think most of it is just fine. But the heart of the lab is in the first 3 problems. I'm not 100% satisfied with it, but it's good enough for the students. I included my solutions. Zach's solutions are in the notebook files for further reference.