Supporting none-1.0 dt about bindsnet

[djsaunde]

Hi @godelicbach,

An easy way to fix this is to create a new Pipeline variable self.sim_time = int(time / dt), and pass this into the encoding functions. Or, we could redesign the encoding functions themselves (which are sorely in need of an update anyway) by having them accept a dt argument as well.

Thoughts?

[djsaunde]

After a bit more thought, I think it makes more sense to have all encoding functions accept a dt argument. For example, in the poisson encoding, the spike train generation must depend on the simulation time step in order to achieve the correct firing rates.

[djsaunde]

This has been resolved by #152.