fails:Array#dig returns #at with one arg
fails:Array#dig recurses array elements
fails:Array#dig raises without any args
fails:Array#dig calls #dig on the result of #at with the remaining arguments
fails:Array#dig raises a TypeError for a non-numeric index
fails:Array#dig returns the nested value specified if the sequence includes a key
fails:Array#dig raises a TypeError if any intermediate step does not respond to #dig
fails:Array#dig raises an ArgumentError if no arguments provided
fails:Array#dig returns nil if any intermediate step is nil
