You can clone with
HTTPS or Subversion.
For devs wishing to test this gem with an external NTLM server (i.e. Windows 2012 Server), I've written up an NTLM Integration Test Plan that will get you started.
I was trying to use Savon pointed at a Sharepoint intranet site guarded by NTLM authentication. The ntlm experimental branch of httpi didn't actually work for me and seems to have gone somewhat stale.
So I switched the ntlm implementation to use rubyntlm which is native ruby, works on all platforms, and supports NTLM v2.