Use balloon notification on Windows from 7 to 8.1

src/common/osVersion.js

@@ -0,0 +1,7 @@
+var os = require('os');
+var release_split = os.release().split('.');
+
+module.exports = {
+  major: parseInt(release_split[0]),
+  minor: parseInt(release_split[1])
+};