add Chromium support for dynamic page rendering.

[Cash111]

Description:

• Add NewHybridRequest for encapsulating a request that uses Chromium.

Example:

func (e *ExampleSpider) StartRequest(req chan<- *tegenaria.Context) {
	for i := 0; i < 20; i++ {
		for _, url := range e.GetFeedUrls() {
			// 生成新的request 对象
			exampleLog.Infof("request %s", url)
			request := tegenaria.NewHybridRequest(url, tegenaria.GET, e.Parser)
			// 生成新的Context
			ctx := tegenaria.NewContext(request, e)
			// 将context发送到req channel
			time.Sleep(time.Second)
			req <- ctx
		}
	}
}