Added ZREVRANGEBYLEX command

[marijngiesen]

Added the ZREVRANGEBYLEX command and tests. Closes #200.

[popravich]

Good catch, thanks.
Please fix flake8 errors (run make flake to see the list)

[codecov-io]

Codecov Report

Merging #201 into master will decrease coverage by -0.1%.
The diff coverage is 98.33%.

@@            Coverage Diff            @@
##           master     #201     +/-   ##
=========================================
- Coverage   95.42%   95.33%   -0.1%     
=========================================
  Files          55       55             
  Lines        7173     7227     +54     
  Branches      584      592      +8     
=========================================
+ Hits         6845     6890     +45     
- Misses        239      244      +5     
- Partials       89       93      +4

Impacted Files	Coverage Δ
aioredis/commands/sorted_set.py	100% <100%> (ø)	✅
tests/sorted_set_commands_test.py	99.58% <97.5%> (+0.03%)	✅
aioredis/commands/transaction.py	82.63% <0%> (-2.09%)	❌
aioredis/pubsub.py	93.12% <0%> (-1.06%)	❌
tests/conftest.py	86.96% <0%> (-1.01%)	❌
aioredis/sentinel/pool.py	79.37% <0%> (-0.78%)	❌
aioredis/commands/server.py	76.59% <0%> (+1.41%)	✅

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[marijngiesen]

The flake8 errors have been fixed

[popravich]

Thanks