There are currently no guidelines provided for using airshipctl behind a
corporate proxy server even though additional configuration is
necessary.
This change adds a simple proxy guide that outlines the requirements for
running airshipctl behind a simple proxy server.
Change-Id: I7b4959e1758ff4dfccdf3aec0e569aa77214bd3e
Signed-off-by: Drew Walters <andrew.walters@att.com>