Remove junk from public key on import via keybase.io

When I submitted my public key via the keybase.io web client, I copied and pasted output from a PGP keyserver web interface. The output included some header information at the top:

```
Public Key Server -- Get "0x9b41907fa373a6d0 "

-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: SKS 1.1.5
[etc.]
```

Not thinking, I just copied and pasted the key with the heading into the textbox on keybase.io. I chose the gpg+curl method, so keybase.io provided me with a command to execute at a command prompt. The command included the text I had pasted in, surrounded by double quotation marks. But, because the text had a double quotation mark in the first line, the command failed (with some unimportant error message that I don't recall) due to the unintelligible-to-curl token 0x9b41907fa373a6d0.

When I figured out what was going on (syntax highlighting to the rescue!), I resubmitted just the PGP public key block to keybase.io, and the shell syntax that was returned executed correctly.

Errors such as this could be avoided in the future if the keybase.io client scanned the submitted text and removed any junk outside the public key block fences.

Start by tracing the keybase.io gpg+curl public-key import flow described in the issue, especially how pasted text becomes the generated shell command. Verify the behavior with input containing keyserver headers and a quoted identifier; done means junk outside the PGP public key block is removed before command generation and the resulting command executes correctly.

Written by the indexing model from the issue text.