This updates MakeMonitor() to take the channel size as a parameter,
instead of reading it from the global `config` object. Unfortunately,
the caller of MakeMonitor() doesn't actually have access to the global,
since it's in a different package (bin vs the root package). Luckily,
there doesn't appear to be a reason to have a buffer in this channel.
This updates the caller to pass a hardcoded size of 1.
Move ZGrab2's main function to a library, and call it in cmd/zgrab2
after importing all of our modules. Consumes of ZGrab2 as a library can
use the same approach to provide custom sets of modules, without having
to hack the build system or reimplement main.
https://github.com/zmap/zgrab2/pull/224
