Working versions of src/scatter.py and src/neldermead.py.

  Though there are docstrings, the comments for neldermead.py
were stripped after I had to un-compile it after accidentally
deleting it.
  Fixed indentation mistake in src/neldermead.py,
which arose because I had to decompile the module.
  Finshed draft of doc/optimizationTutorial.tex.
  Slightly cleaned up the documentation for src/scatter.py.
  Added comments to src/neldermead.py, explaining what's going
on in the function.