DOC remove `` from loadarff docstring

They were showing up in
http://docs.scipy.org/doc/scipy/reference/generated/scipy.io.arff.loadarff.html
MAINT remove (commented-out) testing code from the ARFF reader

Wasn't working anyway, because the "floupi" function doesn't exist.
Also referred to a file that is not shipped with SciPy.
Merge pull request #4245 from larsmans/arff-fixes

Arff fixes