to_excel() removes existing sheet
I am trying to save a dataframe data to two sheets of same EXCEL file :

> > > df.to_excel('C:/FM_temp.xls','sheet1')
> > > df.to_excel('C:/FM_temp.xls','sheet2')

Pandas 0.8.1 deletes the existing 'sheet1' when it saves data to 'sheet2' .

I want to keep both sheets.   Can 'to_excel()' be changed to accept 'append' mode instead of 'replace' mode?
