title: PHPExcel converts dot after writing in comma
body: <p>I generate an Excel file with importing a csv file. In CSV has contents with following numbers<br/> 
  4.0238484<br/>
  5.3833888<br/>
  dot seperated<br/>
  But if I write an Excel file than the column show me the numbers in following format<br/>
  4,0238484<br/>
  5,3833888<br/>
  I want the dot instead of comma.<br/>
  How can I make it?<br/>
  PHPExcel Version 1.7.7</p>