Add support for being able to add port number to IP address in Controller connect method.

Current Behavior

Port number is set to 44818 and cannot be changed.

Expected Behavior

Optionally specify port after IP address in connect method.
e.g. plc.connect('192.168.1.100:5000');

Possible Solution (Optional)

Parse connect IP address string and check for port number. Use port number passed for eip connect. Default to 44818 if no port provided (no change to current operation).

Context

Mapping different ports on a WAN to different PLCs on a LAN.

Steps to Reproduce (for bugs only)

Your Environment

• Package version (Use npm list - e.g. 1.0.6):
• Node Version (Use node --version - e.g. 9.8.0):
• Operating System and version:
• Controller Type (eg 1756-L83E/B):
• Controller Firmware (eg 30.11):