Partial check for invite page, 404 handling

The invite route no longer calls checkInvite, instead just chekcing the
invite exists. This speeds up page loading. the 404 and invalidCode
pages are now loaded when necessary.

main.go

@@ -143,6 +143,7 @@ func main() {
 	router.GET("/getToken", ctx.GetToken)
 	router.POST("/newUser", ctx.NewUser)
 	router.GET("/invite/:invCode", ctx.InviteProxy)
+	router.NoRoute(ctx.NoRouteHandler)
 	api := router.Group("/", ctx.webAuth())
 	api.POST("/generateInvite", ctx.GenerateInvite)
 	api.GET("/getInvites", ctx.GetInvites)