added binning function to core.py

renamed binspikes -> _binseries
new binspikes taken from spikeclasses
adding better evtsplit to core.py
smoothing added
getting_started_spikes now passing
got ride of spikeclasses.py
refactored decimation
more refactoring in core.py
refactoring bandlimit code
splitting core into smaller modules
LFP_cleaning works
time-frequency notebook runs correctly