Mailplane 2.5.6 released

Release notes:

• NEW: Support for the new Gmail attachment uploader featuring a progress bar (doesn't need Flash anymore)
• FIX: Support for Safari 5.2 beta
• FIX: File attachment problems.
• FIX: Discard message (Command-Option-X) opened the new Gmail label menu
• FIX: Save/Discard button
• FIX: Rare crash on startup when using Mailplane on Snow Leopard.