0.0.4 March 1 2015

• Added worksheet_set_margins() function to set top, bottom, left and right
  margins in a worksheet.
• Fix for issue where format objects were written to the file in the order of
  creation rather than the order of use. This issue caused incorrect formats
  in cells.
  Issue #3.
• Fix for issue where tmp files in constant_memory mode weren't closed
  until application exited.
  Issue #1.