Increase numpy version

setup.py

@@ -85,7 +85,7 @@ setuptools.setup(name='pystencils',
                  author_email='martin.bauer@fau.de',
                  url='https://i10git.cs.fau.de/pycodegen/pystencils/',
                  packages=['pystencils'] + ['pystencils.' + s for s in setuptools.find_packages('pystencils')],
-                 install_requires=['sympy>=1.2', 'numpy>=1.7.0', 'appdirs', 'joblib'],
+                 install_requires=['sympy>=1.2', 'numpy>=1.13.0', 'appdirs', 'joblib'],
                  package_data={'pystencils': ['include/*.h',
                                               'backends/cuda_known_functions.txt',
                                               'backends/opencl1.1_known_functions.txt',