Updated error message when forwarding WebSocket events

[Xemdo]

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Problem/Feature

Closes #309

Description of Changes:

• Updated error message to "Failed to dial RPC handler for WebSocket server; It may not be running. See twitch event websocket --help for help on starting the WebSocket server."

Checklist

• My code follows the Contribution Guide
• I have self-reviewed the changes being requested
• I have made comments on pieces of code that may be difficult to understand for other editors
• I have updated the documentation (if applicable)