Verify SlurmInterface

[AnderGray]

Some clusters don't allow for --mem-per-cpu definitions. Easy fix by removing the following line from test/hpc/slurm.jl

https://github.com/FriesischScott/UncertaintyQuantification.jl/blob/c3ba440caf0116d725a974549f014b27c1d15d11/test/hpc/slurm.jl#L158

[FriesischScott]

I was thinking, maybe instead of verifying that the cluster connection works properly through the tests we export a function like this

function test_slurm_connection(account::String, parition::String),

which will run the same simple "external" model we do in the test now and inform the user that everything works as expected. This should also be easier for the user since no environment variables need to be set and it can be run independently from the rest of the tests. Thoughts?

[FriesischScott]

I'm going to refactor the tests we have into a function that is passed a SlurmInterface and verifies that everything works as expected.