* replace nanoflann with original kdtree
* replace KdTreeOMP in python binding
* include array to fix build error on windows
* add kdtree test with synthetic data
* add nowait to see if it fixes error on win
* update README
* use openmp atomic
* revert. MSVC does not support openmp very well...
* disable parallel kdtree construction on windows
* update README
* rephrase
* avoid knn result copy
* refactoring