Improve rudimentary platform check

[snim2]

When using resume-model, Krun performs a rudimentary checks to determine whether the benchmark is being resumed on the same machine that it was started on. Currently, this check only checks that the uname of the two machines is identical.

This test should differ between platforms, and it would make sense to refactor it into the classes in platform.py. This may happen as part of #75

For Linux, we could use a strong check such as blkid, which returns a unique ID of the root file system. I guess someone could have installed more RAM between resumes, so this doesn't catch every case, but anyhow @ltratt felt this was overkill and suggested we use hostname, which is available on most (all?) Unix like platforms.

A more detailed fix would check every value in the audit dictionary. However, platform.audit() returns a str, but the audit in the JSON file is a unicode. On my machine I have packages with names that contain acutes and other accents, and a == between "this" platform and the previous one always returned False. The Internet contains a wide variety of solutions to this problem, and I didn't get any of them to quite work: hence the current hack.

[ltratt]

I must admit, I was never unconvinced that this is either necessary or feasible; and your travails have probably reinforced that feeling!

[vext01]

You mean you were never convinced, right? I think so :)

[ltratt]

Oops, yes!