* cosmo.el (cosmo--params, cosmo--get-ocurvature, cosmo--write-calc):
  Add curvature and radiation parameters. Curvature is automatically
  computed as derived parameter, given Friedmann's equations.

* cosmo.el (cosmo--efunc, cosmo--get-hubble, cosmo-hubble): Introduce
  Hoggs E(z) function, taking into account also the newly introduced
  parameters.

* cosmo.el (cosmo-calculator): Instead of opening a special-mode
  buffer, open a normal buffer. The special mode buffer was
  problematic because if cosmological parameter were updated while the
  special buffer was already open, it would not update. The user would
  have need to kill it and call again `cosmo-calculator`.