CAnnot find joblib in supervised continuous test

[njohnso6]

https://github.com/GenoML/genoml2/blob/8040f2b1b460cc6085527e5fd65963518459cd11/genoml/cli/continuous_supervised_test.py#L45

When run in supervised continuous test I get the error that amounts to cannot find refModel_prefix.joblib I did this rather than a pull request since I know the discrete version has been tested plenty of times. For continuous, I fixed this by running the rest of the code in this on my own, and tweaking line 45 to read infile_model = refModel_prefix + ".trainedModel" ".joblib"