Errors when running tests internally

[timmyfaraday]

When running the tests internally, many tests fail due to

SystemError: opening file "/Users/tvanacke/.julia/packages/PowerModelsDistributionStateEstimation/QCTn0/test/data/enwl/measurements/temp.csv": Permission denied

[MartaVanin]

This is annoying, we can't make sure that directory has write access for each user.
I see two possible solutions:

1. We either save and store a measurement CSV for each test, or
2. we create a temporary directory with write access with "cd(mktempdir())". I would suspect this might also create issues, but it actually seemed to work here: loading test requires writable cwd JuliaLang/julia#17829

I will try the second one tomorrow or so

[MartaVanin]

I merged to master my branch with the 2. solution, testing works locally for me, but it was also the case before, so would be great if you could check whenever you have a minute

[MartaVanin]

closed by #28