Update GridMap link in README

Author: dan-blanchard

README.rst

@@ -24,7 +24,7 @@ DRMAA Python
 `read the docs <http://drmaa-python.readthedocs.org>`__.  
 
 If you simply want to run Python functions on a DRMAA-compatbile grid, use
-`GridMap <https://github.com/EducationalTestingService/gridmap>`__.
+`GridMap <https://github.com/pygridtools/gridmap>`__.
 
 Requirements
 ~~~~~~~~~~~~