Updating the error message when arrayfire libraries isn't found

- Emits the link to the wiki page which discusses the environment variables

Author: pavanky

arrayfire/library.py

@@ -376,7 +376,8 @@ def __init__(self):
                 pass
 
         if (self.__name is None):
-            raise RuntimeError("Could not load any ArrayFire libraries")
+            raise RuntimeError("Could not load any ArrayFire libraries.\n" +
+                               "Please look at https://github.com/arrayfire/arrayfire-python/wiki for more information.")
 
     def get_id(self, name):
         return self.__backend_name_map[name]