Review usability of NeuralynxIO

[JuliaSprenger]

based on samuelgarcias comment here: NeuralEnsemble#345 (comment)

I very recently try to use this IO but get into problems with cachedir. I don't remember exaclty.

Since I need only to acces AnalogSignal with original dtype (int16) I rewrote this by myself.

My code is really fast because it use mmap and is able to read chunk very fastly.
The code is here at the end of the file:
https://github.com/samuelgarcia/tridesclous/blob/master/tridesclous/datasource.py

maybe the 2 codes could be merge one day.