Python version doesn't support a single phenotype

[regevs]

When trying to load a phenotype file with a single phenotype, you get:

Traceback (most recent call last):
  File "/home/ec2-user/git/feather/permutation_testing.py", line 468, in <module>
    for i in trange(phenotypes.shape[1]):
IndexError: tuple index out of range

This is because np.loadtxt returns a 1-d array in this case.

[dleopold]

The python version also throws an error with a single continuous covariate.