 Dyer is designed for reliable, flexible and fast web-crawling, providing some high-level, comprehensive  features without compromising speed.

 By means of event-driven, non-blocking I/O [tokio] and powerful, reliable [Rust programming
 language], inspired by [scrapy], `Dyer` provides some high-level features.  

 * asynchronous, concurrent streamimg and I/O, make the best of thread pool, network, and system
 resource.
 * event-driven, once you set the initials and recursive generator of `Task`, `Dyer` will handle
 the rest of it.
 * user-friendly, considering the philosophy of rust programming language, more source code,
 proper framework may contribute the awkwardness when efficiency and learning cost are taken
 into consideration. `Dyer` presents high-level wrapper for convenience.    
