grid api

should something be returned here? it seems like we should let the user know that it worked! it's a pretty important operation.

do we need to allow users to delete from python right now? (should we?) i just want to make sure folks won't make a mistake and delete something on plotly by accident.

the only + i can see to allowing this is that we might be able to relinquish a grid name then, which could definitely be useful.

not exactly sure how i feel about it.