Make token optional?

[maple3142]

I think forcing token be required and at least 16 chars is inconvenient to use, because I'd like to use it as a ngrok replacement. This commit maple3142@57be221 is my attempt, which works without token. However, I am not familiar with golang, so I am not sure if this is correct (Doesn't introduce new bug on other features).

[rshade]

Interesting concept. And then you are just calling the endpoint without /_token/? I would probably add a --disable-token requirement to not create a regression.