Add ZipReader and XmlStreamReader
Update .gitignore
Try add a new class QXlsx::Document
Add read xml function for Relationships
Using QXlsx::Document instead of QXlsx::Workbook
Able to read the document properties back now!
Update the readme file
Make constructor of Workbook private
Add read xml function for SharedStrings
Add convenient function saveToXmlData() for worksheet
Refactor QXlsx::Styles and QXlsx::Format
Make that QXlsx::Document is the only subclass of QObject
wip: Add read function for workbook
Fix issue 4: Fix background color of solid pattern

For a solid fill, Excel reverses the role of foreground and
background colours
Fix issue 3: QXlsx::Worksheet::setColumn should use 0-based index
Add basic document files
Introduce macros for namespace to make qdoc happy

qdoc doesn't work for class located in normal namespace
Update the index page of the documentation
Add link to the documentation index page