Implement syncrhrony metrics

[alejoe91]

Replaces #1205

@musall @Moritz-Alexander-Kern

Implements synchrony metrics low-level, without depending on elephant.

Default values for synchrony sizes are 2, 4, and 8. Sizes <= 1 throuw an error, as every spike will have a complexity of at least 1.

TODO

• Add function to add syncrhonous events to existing sorting (might be useful)
• Add tests: assess if syncrony metrics increase with added levels of synchrony

[zm711]

couple typo suggestions, and a wording clarification.

[alejoe91]

@samuelgarcia thanks for the tip! The implementation with np.unique is indeed faster (only 4X)

[alejoe91]

@samuelgarcia is this ok to merge?

[samuelgarcia]

@musall @Moritz-Alexander-Kern : would you have time to look to this to valide that this new code correcpond to the method ?

[alejoe91]

@musall @Moritz-Alexander-Kern : would you have time to look to this to valide that this new code correcpond to the method ?

I can point to a gist that shows equivalence with the elephant implementation.

[alejoe91]

Here it is:

https://gist.github.com/alejoe91/1a10a10420901599db1cc77789a2f714

[musall]

The code looks good to me.
Thank you for pushing the new implementation!

[Moritz-Alexander-Kern]

I agree, thanks for the implementation.