Upgrade csympy

Author: certik

pkgs/csympy.yaml

@@ -4,8 +4,8 @@ dependencies:
   run: [python, numpy, gmp]
 
 sources:
-- url: http://github.com/sympy/csympy
-  key: git:6af4e859ece7d58c71f3fa2cb702d9363b100d7d
+- key: git:c7308bec766a0d54f3faea5f50d5798ae1b73271
+  url: https://github.com/sympy/csympy
 
 defaults:
   # lib/python2.7/site-packages/csympy/lib/csympy_wrapper.so contains hard-coded path