port circleparse changes

[tybug]

This is a port of the past two years (sounds more impressive than it really is) of changes over at the circleparse fork. After this circleparse will become defunct and circleguard will use osrparse instead.

There are quite a few changes here. The major ones are:

• add scorev2 mod (closes Can't parse replays with ScoreV2 mod #18, supersedes Add scorev2 mod to the mods enum #20)
• mod_combination is now a bitwise enum instead of a list of enums
• support for parsing "pure" lzma strings (no other information available besides the replay data, since the osu! api /get_score endpoint only gives us the replay data and nothing else)
• removal of the very last frame in replays after a certain version. This is the "rng seed" value. See the osu! wiki:

  On replays set on version 20130319 or later, the 32-bit integer RNG seed used for the score will be encoded into an additional replay frame at the end of the LZMA stream, under the format -12345|0|0|seed.

[kszlim]

Since you're the defacto maintainer of osrparse now, I'll leave this up to you, but consider adding type annotations/mypy to this library since you're actively looking at it now. I've always found types pretty handy.

[tybug]

Good point. I've added type annotations to all public-facing members (adding them to internal methods doesn't seem worth the trouble).

[tybug]

@kszlim I'm afraid there's a merge rule setup on the master branch which means I can't merge without an approving review (and I can't approve my own pr). Up to you if you want to remove that rule or if you want to keep a rubber stamp on all future prs.

[kszlim]

@tybug removed it