isc: phaseshift_isc overlaps with brainiak.utils.phase_randomize

[mihaic]

We should not have duplicate functionality.

[snastase]

These are not really functional duplicates. I think in theory what we want is (a) phaseshift_isc, which performs the nonparametric test using phase randomization and returns a null distribution, p-values, etc; and (b) a more generic phase_randomize utility that simply takes in time-series and phase-randomizes them. I think having this phase_randomize utility is useful even outside the context of ISC analysis. And ideally, the phaseshift_isc function should use the phase_randomize function internally. This was a little tricky because the pairwise and leave-one-out ISC approaches apply the phase randomization slightly differently, but should be work now—see #405 (commit dba670a). I've updated phaseshift_isc in isc, utils and tests to match.

[mihaic]

There's a way to close issues with commit messages such that it is clear they were fixed. I think we should use it in the future:
https://help.github.com/articles/closing-issues-using-keywords/