tune.grid_search() should accept iterables

[waleedkadous]

tune.grid_search() does not accept iterables (e.g. range(1,10)).

Thus

search_space = {"max_depth": tune.grid_search(range(1,12)) }

causes an error. I think many people would expect the above to work.

Instead the user has to write:

search_space = {"max_depth": tune.grid_search(list(range(1,12))) }