Two new methods:
- SetSheetViewOptions(sheetName string, viewIndex int, opts ...SheetViewOption) error
- GetSheetViewOptions(sheetName string, viewIndex int, opts ...SheetViewOptionPtr) error

The option values are given by the user through types that have privates methods
that implement the private SheetViewOption and SheetViewOptionPtr interfaces:
- DefaultGridColor(bool)
- RightToLeft(bool)
- ShowFormulas(bool)
- ShowGridLines(bool)
- ShowRowColHeaders(bool)

Examples:
    err := xl.SetSheetViewOptions("Sheet1", -1, excelize.ShowGridLines(true))

    var showGridLines excelize.ShowGridLines
    err := xl.GetSheetViewOptions("Sheet1", -1, &showGridLines)

Fixes #145.

- go test and godoc updated

- go test updated

- Format code and update readme

- Unify the index row number index of functions `SetRowHeight()` and `GetRowHeight()` relate issue #68;
- Unify the return value data type of functions  `SetColWidth()` and `GetColWidth()`;
- go test updated

- gofmted with -s

- Partial logic performance optimization, use pointer reference instead of a pass the variable value;
- Add comments for content types struct definition;
- Update go test `TestSetBorder` section

- Function parameter code is simplified;
- Fix element `Tint` value parsing error in worksheet;
- Update go test

- Add escape characters of sheet name;
- Update go test and fix typo

- New functions `GetActiveSheetIndex`, `GetSheetName` and `GetSheetMap` added.

- Update workbook and sheet relationships and self-close tag replacement hack functions

- Compatibility improved: relationship namespace in `workbook.xml` has been changed (`xmlns:mc`, `xmlns:x15` and `mc:Ignorable` added)

- Fix issue XML tag `headerFooter` and `sheetPr` element self-close errors cause file corruption;
- Fix issue `Section` and `Pane` element order make file corruption in some case;
- Change sheet `rId` calculation method in `/xl/workbook.xml`, fix makes file corruption in some case;
- Compatibility improved: add `xlsxTabColor` struct and some XML element for worksheet

- Update import PKG syntax in struct;
- Update test XLSX file (include table, charts, functions, comments and hyperlink on Sheet1)

- Update test template for this fix

Fix hyperlink missing after save issue and update completion row element logic to enhance compatibility.

1) Update readme file credits and go report badge added; 2) Remove use less function; 3) Update test file.