working cli that handles loading/building oauth2 and making a legato_user

~/.legato.yml needs:

id: ga_oauth2_id
secret: ga_oauth2_secret

And, if you have a token, you can set token: oauth2_token. This obviously expires after some short period of time.

After loading/building oauth2 creds, it will drop you in an irb session. There you will find a method `legato_user` that can be used to load profiles, etc.

It also includes `Legato::Management` into the current session, so you can say `Profile` instead of `Legato::Management::Profile`.