Improve Solver.solve docstring.
Improve Solver.solve docstring.

Signed-off-by: Jamie Townsend <712d3bf917252432b8abdc41edb77e32fa2cc414@gmail.com>

nkoep/pymanopt,tingelst/pymanopt,pymanopt/pymanopt,nkoep/pymanopt,pymanopt/pymanopt,j-towns/pymanopt,nkoep/pymanopt