1. The use of permutations is now consistent with how they are used with
interval exchange transformations already in Sage.

2. Rotating Foliations is done.
1. Finished the method for foliations that calculates the transition
data for restricting to an interval.

2. The lengths of the Arnoux-Yoccoz foliation were in QQbar, because the
stretch factor is calculated of an eigenvalue of a matrix over QQ. This
slowed down the calculation by at least an order of magnitude. This is
now fixed and the calculation is done by floating point numbers.

3. Added a separate _fmod method on top of _mod, because there was an
issue with floating point division. It would be nice later to keep only
one of these.