README: fix typo

Problem: the README has a typo and gives instructions that break.

Fix it.

Author: jameshcorbett

README.md

@@ -19,7 +19,7 @@ mkdir build
 mkdir install
 
 cd build
-cmake -DCMAKE_INSTALL_PREFIX=../install ../kvtree
+cmake -DCMAKE_INSTALL_PREFIX=../install ../KVTree
 make
 make install
 make test