Refactor to default role obj

[bengartner]

Issue #78

Set default_role to obj and refactored out existing :obj: tags. Fixed 3 sphinx warnings for unresolved references and spot checked the docs. I did NOT look at all the defaults being parsed by sphinx, so it's possible some of them have silently changed meaning. I guess the way to check this would be to diff the html output and make sure it's small?

[njsmith]

I guess the way to check this would be to diff the html output and make sure it's small?

I'm not super worried, but if you do this then I bet you'll learn something one way or the other :-)

There are also a lot of places in the docs where we use explicit role markers like :class:`trio.Lock` , that could become a plain `trio.Lock` instead. That doesn't necessarily have to happen as part of this PR, and maybe it's better if it doesn't. But that's where we'll get most of the benefit from having default_role = "obj"

[bengartner]

Diff was small!

[njsmith]

OK, let's put this in and we can worry about reducing :class:/:meth:/etc clutter in followups

I'm also sending a github invite, as described in our contributing documentation. You're not obligated to accept, but we'd certainly love to have you :-)