Mailplane 2.5.4 released

Release notes:

• FIX: Blank/White screen when composing messages or accessing a message draft.
• CHANGE: The 'Advanced Attachment' uploader has been disabled to fix the 'Blank/White' screen.
• FIX: Gmail's New Style didn't work with Mailplane (Command-L; Send/Save Now/Discard buttons; Printing)