small fixes

• small bug fix in worksheet markup
• sheetMode is now public type and named as SheetMode

v1.0.3

Cols/Rows now can accept styles, but not only styleID. Options for cols/rows can hols styles info now.

v1.0.2

up dependencies - SaveAs supports for io.Writer now

v1.0.1

small optimizations for rich texts (fmt.Stringer or custom type with underlaying string type can be used) and streamwriter doesn't require to call Close anymore