make NCBI requests async

[manulera]

closes #96, since those are the slowest ones

[codecov]

Codecov Report

Attention: Patch coverage is 92.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 94.71%. Comparing base (09a93c8) to head (876f215).

Files	Patch %	Lines
ncbi_requests.py	86.36%	3 Missing ⚠️
main.py	96.42%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #181      +/-   ##
==========================================
- Coverage   94.88%   94.71%   -0.17%     
==========================================
  Files           9        9              
  Lines        1349     1363      +14     
==========================================
+ Hits         1280     1291      +11     
- Misses         69       72       +3     

Flag	Coverage Δ
unittests	94.71% <92.00%> (-0.17%)	⬇️

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