Problem: SS can't find p7zip binary when it's called 7z

[sevein]

I've learned today that in the installation instructions of CentOS we ask the user to run the following command:

$ sudo ln -sf /usr/bin/7za /usr/bin/7z

SS doesn't implement a mechanism to fallback to 7za so if the step is missed the appliation will fail. This is an example on how this affected to one of our users: artefactual/fixity#11.

I'm not sure if this should be considered a priority but it wouldn't be hard to solve.