Unclear failure for command line "keybase id" command

I noticed that when I ran

```
keybase id {username}
```

I received a failure code on that user's Twitter identification. I am fairly certain that the issue was simply that the user's Twitter account is private, but it was unclear from the output of the command.

Example:

```
$ keybase id foobar
✔ public key fingerprint: ...
✖ "foobar" on twitter: https://twitter.com/foobar/status/... (failed with code 106)
✔ "foobar" on github: https://gist.github.com/...
```

I would suggest outputting either clearer feedback, or a url which provides possible reasons for the failure.

Start by reproducing `keybase id foobar` with a Twitter account whose verification cannot be fetched, then inspect where the command formats failure code 106. Done means the CLI gives clearer feedback or provides a URL explaining possible reasons for the failed Twitter identification.

Written by the indexing model from the issue text.