Working with snappy behind a ntlm proxy

[Joseph Winston]

At work, I must live behind a ntlm proxy and in the past I used some 
combination of cntlm (http://cntlm.sourceforge.net/) and adding 
HTTP_PROXY and HTTPS_PROXY entries to the Dockerfiles.  And if I was 
using vagrant, I added https://github.com/tmatilai/vagrant-proxyconf 
entries to my Vagrantfiles.

What is the recommend workflow for using snappy in an environment that 
requires ntlm?