#252 AttributeErrors in Connection objects-refactoring problem

[Lutz Paelike]

Probably caused by (unfinished?) refactoring the interface for the Connection object is broken.
In connections.py since revision 530 the Connection class does not inherit from _mysql.connection anymore but makes it a private attribute "_db" which is a good thing i think.

However methods/attributes formerly present in Connection objects by inheritence are not available anymore and don't seem to be exposed at other places.

For example connection.ping() does not work and raises an AttributeError.