Close connections when window closed

Fixes #8

electron.js

@@ -30,6 +30,11 @@ function createWindow () {
   // Open the DevTools.
   // mainWindow.webContents.openDevTools()
 
+  // Emitted when the window is closed.
+  mainWindow.on('close', function () {
+    connectionManager.closeAllConnections()
+  })
+
   // Emitted when the window is closed.
   mainWindow.on('closed', function () {
     // Dereference the window object, usually you would store windows