Doc. says cells can be merged, but how?

Hello,

Several questions:

1°) How can I merge cells in a sheet? I looked in the README and in the source but I couldn't find which method to call.

2°) Can I modify the width of a column to be "optimal width"? If yes, how?

3°) How can I set the format number for a single cell? (I'd like some cells to be numbers with at most 1 digit after the comma).

Thanks for your work!