add --hostname option

[rmaksimov]

@mohemiv noticed that ruler uses predefined value "RULER" while using NTLM authentication
so i have added the --hostname option to specify any value as a host name

[staaldraad]

Could we leave the default value as RULER.

It is one of the IOCs we published for the tool and although easily modifiable, it is worth having as a "script kiddie" or basic detection effort built into the tool.

https://github.com/sensepost/notruler/blob/master/iocs.md#local-host-domain-controllerexchange-server

[rmaksimov]

Sure, I forgot to set it as the default value

[rmaksimov]

It should be noted that the current PR solves only part of a problem (related to your fork of go-ntlm). I'm going to fix this in the near future, but it should be applied in both projects at the same time.
Until then, you can probably leave this PR open

[staaldraad]

Awesome, thanks for the update. Yeah I had a look at updating it in the dependency as well, however this looks like it correctly overwrites the value hard-coded into the defaults. I'm happy to leave it as is, and pull this into Ruler.