Should CI test with CMake 2.8.12?

[bast]

Quoting from #231 231:
"A question: since Autocmake is CMake-version agnostic, shouldn't the tests be run using the oldest supported version aka 2.8.12?"

[bast]

@robertodr I don't know the answer. I think we should define the supported CMake range and test the lower bound or both bounds. I also think that some stuff will fail on 2.8.12 since this was the motivation to curl the pre-compiled CMake. But independently of failing tests we should do the "right thing". Not sure what it is.

[miroi]

I would make the issue more general: since autocmake is heavy cmake dependent, autocmake must know cmake version and deal with it, when necessary - for example, if some tests are not running with a "very old" cmake.

[bast]

The thing is that there is Autocmake (the Python code and some core CMake stuff) and there are modules. We test them and version them (kind-of) together. So I am not sure.

[bast]

We can let the testing discover the CMake version and skip some tests which test modules which require a higher CMake version.