PyManifold does not support new Manifold API

[sonofhypnos]

See: https://docs.manifold.markets/api. I just noticed the tool I used to run with PyManifold does not work anymore. Overwriting the market class to remove the tags and volume7Days attributes fixed things for me (It seems these attributes aren't returned from the api anymore). I didn't take the time to fix all the tests, otherwise I'd submitted a pull-request. BASE_URI should also be changed. Will submit a pull-request if I still use this in the future.

[LivInTheLookingGlass]

Well that's sad. I'm no longer available to work on this, unfortunately, so it'll either fall to you or @bcongdon