keybase decrypt should be a little prettier and have an option to be quieter

Example: the encrypted text is one line with no newline. Notice how the message runs right into all of the keybase user output. Also, there should be an option to reduce the "noise". Maybe -q and -qq, etc.

```
cat file | keybase decrypt

You need a passphrase to unlock the secret key for
user: "keybase.io/harvey "
2048-bit RSA key, ID 910299D983366848, created 2013-09-06
(subkey on main key ID F94E94DC000BBDD7)

This is a test encrypted message, signed.info: Valid signature from keybase user adamgoldberg (tracking remotely & locally)
info: Signed about 3 hours ago (Sat Oct 25 2014 10:47:42 GMT-0400 (EDT))
✔ public key fingerprint: B053 4AF3 A63E F2CE 7D42 A9F1 23A1 7FA0 2D7F 9CE9
✔ "adamgoldberg" on twitter: https://twitter.com/adamgoldberg/status/526019902889791489
✔ "adamgoldberg" on github: https://gist.github.com/4499a8ed2e6f509e307e
✔ "adamgoldberg" on reddit: https://www.reddit.com/r/KeybaseProofs/comments/2kae1m/my_keybase_proof_redditadamgoldberg/
✔ admin of www.agp-llc.com via HTTP: http://www.agp-llc.com/.well-known/keybase.txt
```

Start with the `keybase decrypt` CLI entry point and reproduce the one-line plaintext example to inspect the output boundary. Trace where user and signature information is printed, then define the quiet levels and verify that normal output is separated from plaintext while `-q` and `-qq` reduce noise.

Written by the indexing model from the issue text.