Numerai-reports

- added log of tournament changes (`settings.events`)
- use event log instead of magic numbers
- increase test coverage to >90%
- Fix missing columns and data fetch for rounds using correlation score (jrdi)

- `reputation` report gained a `rank` option, that allows showing the
leaderboard position instead of raw reputation score
- only try fetching rounds/tournaments that actually exist to reduce load
on numerai's backend
- ensure cached leaderboards are invalidated when their status changes
- notify about leaderboard fetches, to avoid the app to appear as hanging..
- update example code
- update tests

- fix import problems

- fix `reputation` calculation

- fix `reputation` report
- `reputation_bonus` is using correlation_score for rounds >= 164
- `reputation_bonus` is using weighted averaging for rounds >= 164
- rate limit requests to the numerai api
- introduce `Leaderboard` class to abstract leaderboard fetching
- allow turning off rate limiting
- test: increase coverage

- added `friends` report - showing correlation of a user's live auroc to other users
- fix `payments` report for rounds >= 158