FIX Sum power across frequencies of interest instead of averaging it
Add tests to compare power in time and frequency domains in fourier mode

Tests fail because there was no scaling and correction for loss of power due to
windowing.
FIX Scaling fourier mode results

Scaling by number of samples and correcting loss of power due to windowing.
Add multitaper mode tests

Testing whether power calculated in the frequency domain matches power
calculated in the time domain across different time windows and different
numbers of tapers.