Parse --port string as an integer

[mattdesl]

The --port command was being passed as a string, causing an equality check to fail since Node is returning it as an integer, and the options.port was a string. With this PR, the port is parsed as an integer, and the warning message goes away.

Before:

Server running at http://localhost:9966 - configured port 9966 could not be used

After:

Server running at http://localhost:9966 

[brandon93s]

This is fixed by #278.