Add MetricFu.with_run_dir to make it easier to test real usage
Add MetricFu.with_run_dir to make it easier to test real usage

One of the problems with the RSpec suite is that it is leaking state from one scenario to another. The leakage seems to be related to MetricFu.run_dir

That is why I think it is useful to have this utility method.

metricfu/metric_fu,metricfu/metric_fu,metricfu/metric_fu