给Guava的EventBus添加StickyEvent功能（未全面测试，引用需谨慎）

static { // Version 0.1
    def stickyEvents = new ConcurrentHashMap<Class, Object>()
    com.google.common.eventbus.EventBus.metaClass.registerSticky = { object ->
        Multimap<Class, ?> methodsInListener = delegate.finder.findAllSubscribers(object)
        delegate.subscribersByTypeLock.writeLock().lock()
        try {
            delegate.subscribersByType.putAll(methodsInListener)
            // dispatch sticky events
            methodsInListener.entries().each { e1 ->
                Class eventType = e1.key
                def wrapper = e1.value

                stickyEvents.entrySet().each { entry ->
                    Class candidateEventType = entry.key

                    if (eventType.isAssignableFrom(candidateEventType)) {
                        def stickyEvent = entry.getValue()
//                            println("sticky Dispatch $candidateEventType   Want: $eventType  $wrapper $stickyEvent")
                        delegate.enqueueEvent(stickyEvent, wrapper)
                    }
                }
            }
        } finally {
            delegate.subscribersByTypeLock.writeLock().unlock()
        }
        delegate.dispatchQueuedEvents()
    }
    com.google.common.eventbus.EventBus.metaClass.postSticky = { event ->
        synchronized (stickyEvents) {
            stickyEvents.put(event.class, event)
        }
        delegate.post(event)
    }
}

已知BUG：stickyEvents是全局的，实际上每个EventBus需要独立的stickyEvents。由于项目中只需要EventBus单例，同时也没有特别好的解决方法，暂时先这样。

原则No.1：代码美观