Make conventions uniform across tutorials

[brahmaneya]

Test Plan
tox passes

[vincentschen]

This is awesome! Sadly, looks like a bunch of stuff changed from underneath before we could merge this — maybe a rebase and then another pass would help?

[vincentschen]

I'd expect there to be some related changes in the slicing tutorial related to naming (features, pred_test, etc.) — let's do a quick pass there?

[brahmaneya]

I'd expect there to be some related changes in the slicing tutorial related to naming (features, pred_test, etc.) — let's do a quick pass there?

There are no changes there because I've changed other things to be compatible with it (features / vectors ->X_, Y_preds -> preds).

[vincentschen]

from snorkel.utils import preds_to_probs

preds_test = sklearn_model.predict(X_test)
probs_test = preds_to_probs(preds_test, 2)

I see this line in the tutorial — but I think that's it! Otherwise, LGTM