Add script for detecting Kippo SSH Honeypots

[Varunram]

Made changes suggested at #72
Added missing require statement.

[fgeek]

What version did you use when you tested this script? I tested this with Debian 8.7 (stable) and Kippo's git, but kippo-ssh-honeypot.nse didn't find anything. For normal SSH service it says:

Initiating NSE at 19:59
NSE: Starting kippo-ssh-honeypot against 10.0.0.55:22.
NSE: kippo-ssh-honeypot against 10.0.0.55:22 threw an error!
ERROR
stack traceback:
	[C]: in local 'try'
	...o/build/bin/../share/nmap/scripts/kippo-ssh-honeypot.nse:24: in function <...o/build/bin/../share/nmap/scripts/kippo-ssh-honeypot.nse:21>
	(...tail calls...)

Completed NSE at 19:59, 0.65s elapsed

[Varunram]

A pretty old version of kippo actually. But that shouldn't matter since there were no significant changes to kippo after that. Will test and update comment

[fgeek]

Okay thanks. I can retest also in different environment if needed.

[Varunram]

Found the catch. Looks like it was patched, but a different exploit described at http:https://morris.sc/detecting-kippo-ssh-honeypots/ should work. Working on it

[fgeek]

We should add syntax for the both of these to have better coverage. If the payload works we can make some assumption about the running version. If you can tell me the version numbers I can test that the NSE scripts works with both. I'm in #nmap Freenode if you want to chat for faster feedback :)