improve documentation (etc) of totallyreal_rel

[was]

Here is a (small) patch which includes some explanation and references in the docstrings for totallyreal_rel.py.

The roundoff error is a bit mystifying to me, but in any case I
believe I fixed it in the patch: just expanding the bounds works, and seems to only slow it down by a small amount.

In truth, I think the issue has to do with the fact that math.floor
and math.ceil return float64 not ints, and so I have to coerce these
ints, but I couldn't verify this.


 -- John Voight

[kcrisman]

Just a couple comments on non-mathematical things... I think there is now a new reference system with .. , as Minh has recently noted in the developer guide, and "Parallelepiped" seems to be the most common spelling and is the one in my dictionary, though see the Wikipedia article for other, less common, spellings.