feat: Added support for ADDHASH command

[dipinarora9]

1. Added support for ADDHASH command.

2. Fixed _with_schema undefined error occurred on using a cursor as an argument in aggregate function.

3. Added support for deletion of actual document while using delete_document function.

4. Added tests for addhash and Aggregations.

5. Fixed errors in reducer.py.

[ashtul]

Thank you for your contribution.
Everything looks in order.

Can you please add a test for add_hash and for aggregate with schema?

[dipinarora9]

Okay, I'll add the tests for both.

[codecov]

Codecov Report

Merging #69 into master will increase coverage by 0.90%.
The diff coverage is 86.76%.

@@ Coverage Diff @@ ## master #69 +/- ## ========================================== + Coverage 89.58% 90.49% +0.90%  ========================================== Files 12 12 Lines 1402 1462 +60 ========================================== + Hits 1256 1323 +67  + Misses 146 139 -7 

Impacted Files	Coverage Δ
redisearch/client.py	85.33% <66.66%> (+2.88%)	⬆️
redisearch/reducers.py	100.00% <100.00%> (ø)
test/test.py	98.28% <100.00%> (+0.15%)	⬆️
redisearch/aggregation.py	76.04% <0.00%> (+1.79%)	⬆️

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[dipinarora9]

Hey @ashtul ,
I have added the tests for addhash and aggregations.