Use `defaults write` to create a plist file for Yosemite compatibility

`make new property list file` does not work in Yosemite unless the file already exists. This change initializes the plist file with a garbage value that is overwritten by `make new property list file`.

Unfortunately, there are more serious issues with UI automation in Yosemite that cripple [my workflow](/idpaterson/alfred-wunderlist-workflow), but this one was resolvable. Thanks @surrealroad for the suggested fix!