Use any port number if specified to initialize client

[ben-walczak]

The company I work for is currently using this client, but we are providing our certificate on a different port number. So, the only way to fix this issue is to provide a way to insert our own port number to match which port we serve our certificate.

Potential changes: Make changes to pass port_number in with a default value of 17778. Then do a string insertion into the url to specify the port number wanted. The change would be located here:
https://github.com/solarwinds/orionsdk-python/blob/master/orionsdk/swisclient.py#L14 (and line 15)