Check for a modal window being onscreen before trying to put up the Sparkle prompt.
Updated changelog
Merge pull request #426 from alfwatt/master

Check for a modal window being onscreen before trying to put up the Spar...
Fix sandbox service name macro.
Get the sandbox service linking.
Silence warnings.
Follow Sparkle naming conventions.
Fix build phase configuration for sandbox service.
Embed sandbox service bundle directly in the Sparkle framework.
Turn new appcast attributes into constants.
Remove references to JSON appcasts which will not be supported.
Use dedicated APIs for retrieving/comparing operating system versions.
Merge branch 'master' into yahooxpc