Version bump.

README.md

@@ -72,7 +72,7 @@ The **performance measurement tool** can be compiled with:
 
 ````g++ -std=c++20 -mavx -Ofast tiny_bvh_speedtest.cpp -o tiny_bvh_speedtest````
 
-# Version 1.3.0
+# Version 1.3.1
 
 Version 1.3.0 changed the names of vector math functions, which are now prepended with ````tinybvh_````, e.g. ````tinybvh_cross````, ````tinybvh_normalize````. This avoids name clashes in applications that override the vector types with their own. Basically tinybvh evades these so you don't have to.