Use redis universal client in token bucket

[BrianLeishman]

Updated the client to a UniversalClient, which works for redis pools as well as single redis servers.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 83.51%. Comparing base (50bb6c3) to head (844d499).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #34 +/- ## ======================================= Coverage 83.51% 83.51% ======================================= Files 10 10 Lines 1468 1468 ======================================= Hits 1226 1226 Misses 169 169 Partials 73 73 ```

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[BrianLeishman]

@mennanov makes sense to me, done!

[mennanov]

Thanks for contributing!