replaced canonical evaluation by faster pure-numpy version

This solves issue #32 (closed).

The current numba based implementation is replaced by a pure-NumPy version. This is more easy to read, and has a better performance compared to the numba-version for the parameter space dim<=6,deg<=10,lp<=3 (see here).

The unit test of polynomial evaluation in canonical form was replaced by a naive one using plain python loops. This reflects the fact, that the new pure-NumPy implementation is based on the current implementation of the unit test.