BLD: #517 friendlier setup message with no numpy

Author: gregglind

setup.py

@@ -32,7 +32,14 @@
         'install_requires': ['python-dateutil < 2','numpy'],
     }
 
-import numpy as np
+try:
+    import numpy as np
+except ImportError:
+    nonumpy_msg = ("# numpy needed to finish setup.  run:\n\n"
+    "pip install numpy  \n# or easy_install numpy\n") 
+    print nonumpy_msg
+    import sys
+    sys.exit()
 
 # from numpy.distutils.core import setup