Version 2.1

[New Features]

• Ability to hide the collection sidebar from the view menu
• Polish traslation added (thanks to MCbx)

[Improvements]

• Dropbox API migration to v2 (v1 will stop working by 2017-06-28)
• Updated Qt to 5.9 (User interface library) for better compatibility with Windows 10 and macOS Sierra

[Bug Fixes]

• Fixed crash when adding a new collection
• Collection list is not updated correctly when a new collection is added or deleted