Multiprocessingspider

Refactor
- Remove property "name" from "FileDownloader".
- Complete class "UserAgentGenerator" in "MultiprocessingSpider.Utils".
- Continue to optimize the setter method of each property. An exception will be raised if the value is invalid. "sleep_time" now can be set to 0.
- Change the sleep strategy of subprocess, subprocess will sleep after receiving the task package to prevent multiple requests from being sent at the same time.
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Bug Fixes
- Fix "start_urls" invalidation.
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Features
- Add overwrite option for "FileSpider".
- Add routing system. After overriding "router" method, you can yield a single url or a url list in your parse method.
Bug Fixes
- Fix retry message display error.
Refactor
- Optimize setter method. Now you can do this: spider.sleep_time = ' 5'.
- Will not resend request when "status_code" is not between 200 and 300.
a) MultiprocessingSpider
- Rename property "handled_url_table" to "handled_urls".
- Remove method "parse", add "example_parse_method".
- "User-Agent" in "web_headers" is now generated randomly.
- Change url_table parsing order, current rule: "FIFP" (first in first parse).
b) FileDownloader
- Remove "add_files" method.
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- The first version.