Move --squirrel-xxxx handling to new file

main/squirrel-win32.js

@@ -0,0 +1,51 @@
+module.exports = {
+  handleArgv
+}
+
+var electron = require('electron')
+
+var app = electron.app
+
+var handlers = require('./handlers')
+
+function handleArgv (cmd) {
+  if (cmd === '--squirrel-install' || cmd === '--squirrel-updated') {
+    handlers.init()
+
+    // TODO:
+    // - Install desktop and start menu shortcuts
+    // - Add explorer context menus
+
+    // Always quit when done
+    app.quit()
+    return true
+  }
+
+  if (cmd === '--squirrel-uninstall') {
+    // Undo anything we did in the --squirrel-install and --squirrel-updated handlers
+
+    // TODO: implement this
+
+    // Always quit when done
+    app.quit()
+    return true
+  }
+
+  if (cmd === '--squirrel-obsolete') {
+    // This is called on the outgoing version of your app before we update to the new
+    // version - it's the opposite of --squirrel-updated
+
+    // Always quit when done
+    app.quit()
+    return true
+  }
+
+  if (cmd === '--squirrel-firstrun') {
+    // This is called on the first run of the app.
+
+    // Do not quit the app
+    return false
+  }
+
+  return false
+}