Merge pull request #3 from charlietsao/patch-1

Fix build command

Author: tsung-wei-huang

README.md

@@ -45,6 +45,7 @@ We use cmake to manage the package. We recommand using out-of-source build:
 ```bash
 ~$ mkdir build
 ~$ cd build
+~$ cmake ..
 ~$ make & make test
 ```