added read_formula hints for ExcelSheet::read(), ExcelSheet::readCol() and ExcelSheet::readRow()
added hint for ExcelBook::setLocale()
fixed typo
changed ExcelSheet doc to reflect read_formula option for ExcelSheet::read(), ExcelSheet::readCol() and ExcelSheet::readRow()
changed 4-spaces formatting with tabs to match original formatting
Merge pull request #73 from johmue/master

added read_formula hints for ExcelSheet::read(), ExcelSheet::readCol() and ExcelSheet::readRow()