* go mod tidy applied

* File.DuplicateRow() method added

- RGBA, HSL color convert has been added;
- go test updated

- Add error return value for functions: `AddChart()`, `AddComment()`, `AddPicture()`, `AddShape()`, `AddTable()` and `SetConditionalFormat()`
- go test has been updated

- Remove useless function `replaceWorkSheetsRelationshipsNameSpace()`;
- Make test cases use strict error checking

- go test updated

Signed-off-by: Ri Xu <xuri.me@gmail.com>

- godoc updated

Signed-off-by: Ri Xu <xuri.me@gmail.com>

- API changed, use worksheet name instead of "sheet" + index, related issue #25, #43, #47, #51, #89, #101, #116 and #120.
- go test updated

- Readme and go test updated

- New function `NewStyle()` added and function `SetCellStyle()` has been exported, relate issue #72;
- go test and go doc updated

Function `GetCellValue()` performance improvement by avoid repeating deserialization, relate issue #70.

- Make function `TitleToNumber()` exportable, note that function `ToAlphaString()` return value calculation changes, get more info from go doc. Relate issue #63;
- Readme and go doc updated

- Function `formattedValue()` performance improvement by avoid repeating deserialization, relate issue #64;
- Make function `ToAlphaString()` exportable, relate issue #63

- Handle pre-defined number format set of cell when set cell value with `time.Time` data type, related issue #62;
- go doc updated

- Simplified code

Priority cell style, when the cell and the column at the same time with the style attribute. Relate issue #54 and #56.

- Function `SetCellValue()` support `time.Time` data type parameter, relate issue #49;
- go doc and go test updated

- Optimize deserialization operations;
- README updated, add go version required notice

Performance enhancements, remove redundant XML element checking logic. Relate issue #29. The benchmark report of the current version of this library is shown on the wiki page.