Attempted an exact solution of T for a given Sigma.
It doesn't work because the solver always returns the trivial
solution, namely T=0 everywhere. I tried to call the function
`fun` when T=0 is being tried with a small offset from zero to
let the solver know that T=0 is not a root we want, but this caused
the solver to fail to converge.
Merge branch 'master' of https://github.com/garmilla/circumbinary