Only use concurrency in console

As pointed out in spatie/fork#4, Fork only works in a CLI environment.

src/ServiceProvider.php

@@ -10,8 +10,8 @@ class ServiceProvider extends LaravelServiceProvider
 {
  public function register()
  {
- $this->app->bind(Tasks::class, function () {
- return class_exists(Fork::class)
+ $this->app->bind(Tasks::class, function ($app) {
+ return $app->runningInConsole() && class_exists(Fork::class)
  ? new ConcurrentTasks(new Fork)
  : new ConsecutiveTasks;
  });