0.3.1 released

Fixed

• Fixed problems about saving or deleting files to the local database (#24, #25).
• Disable version up warning.
• Fixed error on folder renaming (#24).
• Merge dialog is now shown one by one (#25).
• Fixed icons of queued files.
• Handled sync issue of Folder to File.
• Fixed the messages in the setting dialog (one of #28).
• Fixed deadlock.