BUG: can now use 'hyperband' with stacking

[patr1ckm]

We can now use hyperband with stacking, we should not throw an error in create_and_run_model.

@elsander can we hyperband with sparse_logistic or sparse_linear_regressor?

[elsander]

It's not possible to use hyperband with GLMs because of how the algorithm is structured. Essentially, you need some parameter to iterate over (# epochs, # trees) during hyperband, and there isn't a parameter like that for GLMs. Fortunately, they're pretty fast to train anyway, so grid search should get the job done fine :)

[patr1ckm]

Great, thanks!