[pavlokomarov]

This PR adds:

1. HTTP exceptions handling
2. RetryMiddleware, based on HTTP exceptions handling

@ksassnowski please review this changes and help me to draw up this PR, if this functionality are needs in package :)

[ksassnowski]

Thanks for the patience and thanks for your contribution!

In it’s current state, this PR is a little too big and changes too many things at once. I’d like to split this up into several smaller PRs. I think the most important part is adding a onRejected handler for requests. I would like this handler to simply return the response as well instead of throwing an exception. Because it might be useful to write middleware that deal with failed requests/responses.

After that, we can take a look at the kinds of default middleware that would make sense to add to this package. Looking at Scrapy again, an HttpStatusMiddleware that filters out requests with a certain response code could make sense. But this would be another PR.

So if you want to open a new PR that adds an onRejected handler, I would appreciate it. Then, we can work from there :)

I’m going to close this PR, but we can continue discussing the changes here until we have a new PR.