strong-deploy usage should have help for how to provide credentials for an authenticated pm server

[cgole]

For git deploy, user will be asked for cred by the git command prompt. For tar ball deploy there are no instructions on how to provide credentials

[cgole]

instead of HTTP Code: 401 say authentication failure or something similar

[rmg]

TODO:

• [x] Add help text about how to specify credentials.
• [x] Mention auth in the error message when we see a 401 or 403.

[rmg]

@cgole I've merged #22 and it should be available on staging soon for you to verify.

[rmg]

Released, strong-deploy@1.1.4