Revert "gnu: python-numpy: Update to 1.13.1."

This reverts commit 025b196d.

This is necessary as neither the current release nor the latest development
version of python-pandas can be build with numpy 1.13.x.

gnu/packages/python.scm

@@ -3720,21 +3720,22 @@ (define-public python2-rpython
 (define-public python-numpy
   (package
     (name "python-numpy")
-    (version "1.13.1")
+    (version "1.12.0")
     (source
      (origin
        (method url-fetch)
-       (uri (pypi-uri "numpy" version ".zip"))
+       (uri (string-append
+             "https://github.com/numpy/numpy/archive/v" version ".tar.gz"))
+       (file-name (string-append name "-" version ".tar.gz"))
        (sha256
         (base32
-         "1fsgkhh1vdkhmlz8vmdgxnj9n9yaanckxxzz9s0b4p08fqvjic69"))))
+         "025d4j4aakcp8w5i5diqh812cbbjgac7jszx1j56ivrbi1i8vv7d"))))
     (build-system python-build-system)
     (inputs
      `(("openblas" ,openblas)
        ("lapack" ,lapack)))
     (native-inputs
-     `(("unzip" ,unzip)
-       ("python-cython" ,python-cython)
+     `(("python-cython" ,python-cython)
        ("python-nose" ,python-nose)
        ("gfortran" ,gfortran)))
     (arguments