PID loop tutorial.
started section on pid tuning
more detail on tuning a PID loop
adding pid tuning plots.
changed image links so that they work in github directly.
consolidated PID tuning plots into one.
adding more plots for pid tuning.
plot showing tuned pid loop
fixed error on period measurement.
added rocket design image.
resize rocket image
pidloop tutorial is complete. The code examples now need to be verified.
fixed errors in the code examples.
completed PID loop tutorial.
merged changes from a commit on github
fixed some broken links with the tutorials.
Merge pull request #16 from theodoregoetz/master

PID-loop tutorial