natergj/excel4node — pull request #18 by daviesjamie (2014-12-17 14:23:07+00:00)
Title: Add a callback when writing to the filesystem.

The WorkBook write function can now be called in three different ways:

`workbook.write(filename)`
will asynchonrously write the workbook to the specified file.

`workbook.write(filename, response)`
will write the workbook to the node response object.

`workbook.write(filename, callback)`
will write the workbook to the specified file, and call the callback
function when the process has completed (or errored).

This fixes #4.