[oe] Dropping Debian 7 as supported?

[Burton, Ross]

Hi,

I'm proposing that we drop Debian 7 from the supported distributions list
in master, so that the 2.1 release supports Debian 8.  Debian 7 was
released in 2013, Debian 8 superceded it in April 2015 so will have been
out for a year when 2.1 is released, which also means that is when Debian 7
stops receiving security fixes. Nobody should be running Debian 7 after
April 2016!

Any objections?

Cheers,
Ross