Use github.com/mohae/deepcopy to deep copy worksheets instead of the
internal deepcopy function that was using encoding/gob serialization and
deserialization.
Rationale:
1/ using `encoding/gob` is much slower than
[`mohae/deepcopy`](https://github.com/mohae/deepcopy/)
2/ When building an application this implementation of `deepcopy` drags
the `encoding/gob` package into the binary. And this package is much
bigger than `mohae/deepcopy` (which only depends on `time` and `reflect`).
```
$ LC_ALL=C stat -f "%6z %N" $(go env GOPATH)/pkg/$(go env GOOS)_$(go env GOARCH)/github.com/mohae/deepcopy.a $(go env GOROOT)/pkg/$(go env GOOS)_$(go env GOARCH)/encoding/gob.a
10508 .../pkg/darwin_amd64/github.com/mohae/deepcopy.a
541818 .../pkg/darwin_amd64/encoding/gob.a
```
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.
xuri