* cosmo.el (cosmo--get-hubble-distance): Add computation of Hubble
  distance (1/H0 in Mpc).

* cosmo.el (cosmo--get-los-comoving-distance,
  cosmo-los-comoving-distance): Add computation of line-of-sight
  comoving distance and respective interactive function.

* cosmo.el (cosmo--check-param): Fix condition to allow parameters
  equal to zero.