beta3

Various fixes given feedback on the second beta. Notably:

• Logout really do clean cookies on windows
• Missing OSX shortcuts (fullscreen, hide)
• Tooltips on buttons
• Attach image button for non-drag-droppers
• Bug fix writes to app dir (thanks @maxkueng)
• Binaries for win-x64 and linux-x64 (we're in the future after all)