Add dependencies to setup.py

setup.py

@@ -9,5 +9,7 @@ setup(name='float_raster',
       author_email='anewusername@gmail.com',
       url='https://mpxd.net/gogs/jan/float_raster',
       py_modules=['float_raster'],
-     )
-
+      install_requires=[
+            'numpy'
+      ],
+      )