Cleaned up and commented maplotlib examples
Added license and readme and .gitignore

License and readme for my code only.
.gitignore is for everyone.
Cleaned up and documented NumPy examples
Cleaned up SciPy linear system examples
Cleaned up SciPy LTI example and improved README

- Added URL for the slides to the README
- Renamed LTI system example script to match other files
- Cleaned up comments and plots in LTI system example