Adhere to follow_web_links setting when overriding context

[wonderfulspam]

Closes #38.

The solution isn't 100% satisfying as it basically duplicates the categorization logic from linkcheck. It could perhaps be implemented more cleanly by exposing the Category enum but I'm not sure if that would be worth it. Let me know what you think!

I added a test book which is a copy of the "all-green" book except with config and link texts that indicate what the expected result is. TestRun now optionally takes a Config to allow setting follow_web_links to false.

[Michael-F-Bryan]

It could perhaps be implemented more cleanly by exposing the Category enum but I'm not sure if that would be worth it.

If it were any more complex than some_url.parse() then we'd definitely want to deduplicate the logic, but it should be fine for now.

I added a test book which is a copy of the "all-green" book except with config and link texts that indicate what the expected result is. TestRun now optionally takes a Config to allow setting follow_web_links to false.

This is awesome, thank you 🎉