New module: spambot

[chrisforce1]

We need to pick 10 random domains from this list and then, for each domain:

1. perform the equivalent of dig mx <domain>
2. take the first MX entry and resolve it to an IP
3. attempt to connect to the IP on TCP port 25

Suggested output is as follows:

Time      Module   Description
--------------------------------------------------------------------------------
11:26:01  spambot  Starting
11:26:01  spambot  Preparing random sample of Internet mail servers
11:26:02  spambot  Resolving mx1.domain.com
11:26:03  spambot  Connecting to 1.2.3.4:25
11:26:04  spambot  Resolving mx2.domain.com
11:26:05  spambot  Connecting to 2.4.5.6:25
...
11:26:09  spambot  Resolving smtp.blah.com
11:26:10  spambot  Connecting to 3.4.5.6:25
11:26:11  spambot  Finished

We can improve this later to record successes and failures (like with do with the Tor module), but for now it'll be fine to resolve each of these domains to a mail exchanger, then connect to it on TCP port 25.