v0.5.1 released

User-facing changes:

• Albums no longer try to save their window position/size, as this was causing edge cases on Windows that I couldn’t figure out how to fix
• Pathnames are now handled correctly on yet-to-be-saved album files
• You now get a helpful confirmation prompt before trying to close or revert an unsaved file

Internal changes:

• Mac build process cleaned up and made less error-prone
• Displayed version numbers are also more sensible, at least to me