gnu: python-numpy: Update to 1.12.0.

gnu: python-numpy: Update to 1.12.0.

* gnu/packages/python.scm (python-numpy): Update to 1.12.0.
  [source]: Use github instead of sourceforge.
  [native-inputs]: Add python-cython.

  To simplify the handling of dependency cycles (numpy documentation depends
  on matplotlib, which depends on numpy), we split out the documentation into
  a separate package:
  (python-numpy-bootstrap, python2-numpy-bootstrap): Remove variables.
  (python-numpy-documentation, python2-numpy-documentation): New variables.

Signed-off-by: Marius Bakke <mbakke@fastmail.com>