Fix redis import error, clean up README

[codecov[bot]]

Codecov Report

Patch coverage: 78.57% and project coverage change: -0.44% :warning:

Comparison is base (8de6f8b) 98.79% compared to head (ecc6088) 98.35%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #123 +/- ## ========================================== - Coverage 98.79% 98.35% -0.44% ========================================== Files 13 13 Lines 664 670 +6 Branches 76 78 +2 ========================================== + Hits 656 659 +3 - Misses 4 6 +2 - Partials 4 5 +1 ``` | [Files Changed](https://app.codecov.io/gh/vutran1710/PyrateLimiter/pull/123?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Vu+Tran) | Coverage Δ | | |---|---|---| | [pyrate\_limiter/buckets/redis\_bucket.py](https://app.codecov.io/gh/vutran1710/PyrateLimiter/pull/123?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Vu+Tran#diff-cHlyYXRlX2xpbWl0ZXIvYnVja2V0cy9yZWRpc19idWNrZXQucHk=) | `96.55% <40.00%> (-3.45%)` | :arrow_down: | | [pyrate\_limiter/abstracts/bucket.py](https://app.codecov.io/gh/vutran1710/PyrateLimiter/pull/123?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Vu+Tran#diff-cHlyYXRlX2xpbWl0ZXIvYWJzdHJhY3RzL2J1Y2tldC5weQ==) | `97.05% <100.00%> (+0.06%)` | :arrow_up: |

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