Added extra functionality for PyCheMPS2.
Little text error corrected.
Updated headers
Python interface to CheMPS2 added (called PyCheMPS2).
Merge branch 'master' of https://github.com/SebWouters/CheMPS2

* 'master' of https://github.com/SebWouters/CheMPS2:
  Python interface to CheMPS2 added (called PyCheMPS2).
  Updated headers
  Little text error corrected.
  Added extra functionality for PyCheMPS2.