added multiprocessing to gaussian_fit(...parallel=[False,'dask','multiprocessing']...), added deadtime correction to process_psds(...deadtime_correction=True...)) and added OneofEvery to the .dat particle-by-particle files.

added multiprocessing to gaussian_fit(...parallel=[False,'dask','multiprocessing']...), added deadtime correction to process_psds(...deadtime_correction=True...)) and added OneofEvery to the .dat particle-by-particle files. #41