The mailing list servers have a more complex exim config. Put the
routers and transports into ansible variables.
While we're doing it, role variables with an exim_ prefix - since 'routers'
as a global variable might be a little broad.
iteritems isn't a thing in python3, only items.
We need to escape the exim config with ${if or{{ - because of the {{
which looks like jinja. Wrap it in a {% raw %} block.
Getting the yaml indentation right for things here is non-trivial. Make
them strings instead.
Add a README.rst file - and use the zuul:rolevar construct in it,
because it's nice.
Change-Id: Ieccfce99a1d278440c5baa207479a1887898298e
4cca3f8d2a