pybind11 3.0.0 required.

[hunghaoti]

pybind11>=3.0.0 is required after PR #672 .

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 32.10%. Comparing base (4d95705) to head (29af7f3).
⚠️ Report is 12 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #720      +/-   ##
==========================================
+ Coverage   31.99%   32.10%   +0.11%     
==========================================
  Files         215      215              
  Lines       36192    36218      +26     
  Branches    14520    14540      +20     
==========================================
+ Hits        11578    11627      +49     
+ Misses      22713    22668      -45     
- Partials     1901     1923      +22     

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[IvanaGyro]

I feel we should not install build tools and dependencies in CMake as possible. Doing that makes dependencies hard to be maintained and all new contributors may make mistake easily. Currenctly, including CMake files, there are three places declaring pybind11 dependency.