Edit python scripts.

* Add Olivier as an author.
* Add options u_lim and v_lim for plotVelocity.py.
* Add more files/folders to .gitignore.
* Change variable temp to previous_mean.
* Remove unnecessary options from plotVelocity.py.
* Make plotVelocity.py work without X.
Rename files using American spelling.
Edit Python scripts.

* Remove extraneous lines.
* Start all vorticity plot files names with vort.
* Make default infile in rotateBody.py same as output of naca00xx.py.
* Edit .gitignore.