…ate.

Apparently convention is that object methods return a copy of the object and
that methods are described using the noun form when doing so and the verb
form when modifying in place. These functions have been renamed and altered
to return copies to reflect this convention. The helper functions have been
hidden from the public API using underscore.

`cvxopt` returns a 2D array whereas `scipy` returns a 1D array. 1D arrays
are more versatile because they don't need transpositions.

The third case for defining a rotation, supplying a matix, was undocumented.
Now it is documented with epytext. Additionally, the u and v parameters are
now keyed, and the function enforces valid combinations of parameters.

Translation method docs edited for brevity using markup to link docs.

Rotation method docs rewritten to more clearly define what types of
rotations can be expressed through the given parameters. Documentation
was added to the class method rotations.

After some further reading, defining the rotation angle as twice the
angle between the two provided vectors removes ambiguous cases such as
collinear vectors facing opposite directions.

Broke the u, v parameter for the rotation function into two separate
parameters: i, j for the identity basis vector indices and the u, v
for the vector specification.