os.path.join is getting inputs with slashes in some cases

[jacobtylerwalls]

In a few places we're providing our own forward slashes to os.path.join(), which will probably break on windows.

in settings:

arches/arches/settings.py

Line 397 in c6b043a

"STATS_FILE": os.path.join(ROOT_DIR, "..", "webpack/webpack-stats.json"),

in tests:

arches/tests/exporter/datatype_to_rdf_tests.py

Line 55 in e9e5033

with open(os.path.join("tests/fixtures/resource_graphs/rdf_export_{0}.json".format(model_name)), "r") as f:

Could use a quick grep to see if there are others.