Merge pull request fffaraz#570 from egpbos/patch-1

Add xtensor to Math category

Author: fffaraz

README.md

@@ -523,6 +523,8 @@ A curated list of awesome C++ (or C) frameworks, libraries, resources, and shiny
 * [Vc](https://github.com/VcDevel/Vc) - SIMD Vector Classes for C++. [BSD]
 * [Versor](http://versor.mat.ucsb.edu/) - A (fast) Generic C++ library for Geometric Algebras, including Euclidean, Projective, Conformal, Spacetime (etc).
 * [Wykobi](http://www.wykobi.com/) - A C++ library of efficient, robust and simple to use C++ 2D/3D oriented computational geometry routines. [MIT]
+* [xtensor](https://github.com/QuantStack/xtensor) - A C++14 library for numerical analysis with multi-dimensional 
+array expressions, inspired by NumPy syntax. [BSD 3-clause] [website](http://quantstack.net/xtensor)
 
 ## Memory Allocation