Added an ANSIBLE_CONFIG variable to poteentially override
~/.ansible.cfg
Used os.path.expanduser against all paths that might be read in to allow
~ to be used in config files. I'd have preferred it if os.path.expanduser
took None as an argument but it doesn't.

If remote_port *is* set in the ansible config file, then it will be
interpreted as a string (at which point ssh.connect fails with an
obscure message). Most other numeric variables are handled by
the OptionsParser which takes a type variable when setting up the option -
but remote_port is not an option, so never cast to int.

It might be worth adding a type field to get_config that defaults to a string.
That could be e.g. file or int, which then casts it correctly.