The tests in /tests should do actual http

[HelgeKrueger]

It should be possible to adapt the tests in /tests to do actual HTTP. A few things will be necessary for this:

• Start bovine_blog as an actual server best reachable through a domain name one can configure. So http://bovine.local/ would work as a domain.
• Probably even start an external instance to do the posting from, so something like http://bovine.external/activitypub/user#main-key is resolvable. Otherwise it might be hard to test stuff like HTTP Signatures
• Rewrite /tests/utils/blog_test_env in order to use this setup

It should not be necessary to actually touch the tests. At least once bovine 0.1.0 is released.

The main goal of this would be to be able to run this test suite against any valid ActivityPub implementation (it replaces bovine.local) and the suite should pass.

Of course, this assumes that bovine flavored Client To Server is implemented. E.g. the eventSource test only works if an eventSource is implemented.