Encrypted messages are too long, should be broken into multiple lines

When I use `keybase encrypt`, the result is one giant long line, like:

```
BEGIN KEYBASE SALTPACK ENCRYPTED MESSAGE. 1234567890abcdef 1234567890abcdef …etc… END KEYBASE SALTPACK ENCRYPTED MESSAGE.
```

The problem is, this can be very long. If someone sends me this, I can't copy/paste it into my terminal to `keybase decrypt` it. The paste output gets stopped after 1024 characters, and I'm no longer able to add anymore input. I assume this is a Bash limitation, as it doesn't matter which terminal program I'm in or which CLI command I'm pasting into (keybase, cat, etc.)

GPG, on the other hand, encrypts messages into multiple lines, so this is never an issue.

Can Keybase make it so that encrypted messages are multiple lines and never have more than 1024 characters in each line so that they can be pasted into terminals for decryption, please?

Start by tracing the output produced by `keybase encrypt` and the input accepted by `keybase decrypt`; the issue provides no source files or tests. Check how Bash paste limits affect the encrypted message, then verify that wrapped output with lines no longer than 1024 characters remains decryptable.

Written by the indexing model from the issue text.