Document dependencies

Author: adamjstewart

Diff for: requirements.txt

@@ -1 +1,2 @@
 matplotlib
+numpy

Diff for: setup.py

@@ -44,6 +44,8 @@ def run_tests(self):
     ext_package='cmocean',
     scripts = [],
     keywords = ['colormaps', 'oceanography', 'plotting', 'visualization'],
+    setup_requires=['setuptools'],
+    install_requires=['matplotlib', 'numpy'],
     tests_require=['pytest'],
     extras_require=extras_require
     )