Adjusted det(unitary) = -1 for the logarithm.

Due to the rotation to natural orbitals, the determinant of certain blocks in the unitary can become -1 instead of +1. The logarithm of that block is then complex-valued.. The logarithm of that block is then complex-valued... Swapping the sign of an orbital resolves this issue completely.
The tensors required for the two-orbital mutual information.
Two-orbital mutual information is now added.
Printer for the correlation functions and mutual information.
Little error corrected
Reshuffling stuff as a prelude to Edmiston-Ruedenberg.
Added the EdmistonRuedenberg class.

This class is able to localize orbitals, based on the Edmiston-
Ruedenberg cost function and an augmented Hessian Newton-Raphson
optimizer.
Added test9 to README.md
Irreps table now also in gh-pages.
Localization and ordering of the active space added for DMRGSCF.
Print the correlations and two-orbital mutual info during DMRGSCF
Installation instructions
Install instructions
Added the singlet diradical correlation function
Merge branch 'master' of https://github.com/SebWouters/CheMPS2

* 'master' of https://github.com/SebWouters/CheMPS2:
  Added the singlet diradical correlation function
  Install instructions
  Installation instructions
  Print the correlations and two-orbital mutual info during DMRGSCF
  Localization and ordering of the active space added for DMRGSCF.
  Irreps table now also in gh-pages.
  Added test9 to README.md
  Added the EdmistonRuedenberg class.
  Reshuffling stuff as a prelude to Edmiston-Ruedenberg.
  Little error corrected
  Printer for the correlation functions and mutual information.
  Two-orbital mutual information is now added.
  The tensors required for the two-orbital mutual information.
  Adjusted det(unitary) = -1 for the logarithm.