Fixes Client.Delete() behaves opposite to spec. Deprecates Client.Delete() in favor of Cliente.DeleteDocument() for RediSearch >=v2.0

[TropicalPenguin]

• Fixes Client.Delete() behaves opposite to spec for v1.4 and v1.6 #82
• Deprecates Client.Delete() in favor of Cliente.DeleteDocument() for RediSearch >=v2.0
• Increases the overall coverage

[codecov]

Codecov Report

Merging #80 into master will increase coverage by 0.22%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #80      +/-   ##
==========================================
+ Coverage   77.06%   77.29%   +0.22%     
==========================================
  Files          13       13              
  Lines        1273     1277       +4     
==========================================
+ Hits          981      987       +6     
+ Misses        232      231       -1     
+ Partials       60       59       -1     

Impacted Files	Coverage Δ
redisearch/client.go	79.69% <100.00%> (+0.72%)	⬆️

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[filipecosta90]

@TropicalPenguin thanks you for bringing this up. Took the chance and also added some more tests to it, and deprecated Delete() given that on redisearch >= v2.0 FT.DEL always deletes the underlying document.