Probe transform and decoders

Can now probe `transform` and `decoders`. Changed some of the learning tests to use these probes to ensure that some kind of weight changes are happening. Check out the plots produced by these tests, they're kind of interesting!
Probably not necessary, but it might not be a bad idea to filter here as well. I want to get users in the habit of filtering whenever they downsample, otherwise one can get uncharacteristically noisy outputs.