ensure note is always unique to allow logins on multiple machines

This appends the current date to prevent validation failures due to a token already existing for a given name (try authing the same command on two computers or nuking your local config without nuking the token in github to see what I mean).
```js
{"message":"Validation Failed","documentation_url":"https://developer.github.com/v3/oauth_authorizations/#create-a-new-authorization","errors":[{"resource":"OauthAccess","code":"already_exists","field":"description"}]}```