Changes defaults for ExcelSpreadsheet module
Changes defaults for ExcelSpreadsheet module

* header_present defaults to False
* the sheet defaults to the first one in the workbook

hjanime/VisTrails,celiafish/VisTrails,hjanime/VisTrails,celiafish/VisTrails,minesense/VisTrails,hjanime/VisTrails,Nikea/VisTrails,celiafish/VisTrails,celiafish/VisTrails,Nikea/VisTrails,hjanime/VisTrails,Nikea/VisTrails,minesense/VisTrails,VisTrails/VisTrails,minesense/VisTrails,VisTrails/VisTrails,minesense/VisTrails,Nikea/VisTrails,minesense/VisTrails,hjanime/VisTrails,VisTrails/VisTrails,VisTrails/VisTrails,VisTrails/VisTrails