Display success message at the end of the process

[philnash]

There should be a message displayed at the end of the process with the next steps.

Those next steps are:

• Change into the directory you just created
• Start a local server running the functions: npm start
• Visit the example function at http://localhost:3000/example
• Create new functions in the functions directory and new assets in the assets directory

Use boxen for display, like twilio-run.