Add tr inputs_wrapper and td wrapper, for horizontal layout of inputs inside a table
Support Form#inputs :nested_inputs_wraper option

This makes it possible to separate the inputs_wrapper used for the
the current inputs call, and the one used for inputs calls inside
the block.
Make table inputs_wrapper accept a :labels option and automatically set up th tags with the labels for each column
Add subform :grid option in Sequel plugin, for more compact editing of nested *_to_many associations

This allows you to edit multiple nested objects in a single table,
with one row per nested object and one column per field, with the
labels for each input as table headers.