Look for config file in ~/.azuresmr when running tests

[yueguoguo]

Should settingsfile <- system.file("tests/testthat/config.json", package = "AzureSMR") be replaced by settingsfile <- getOption("AzureSMR.config") in the testing scripts? @andrie

[andrie]

Yes, ultimately it should.

Right now it has the benefit that the file used for settings is in the same location as the package, making it easy to manage your test settings with the package.

However, this fails R CMD check.