doc: modify the install document

ivanszl · ivanszl · commit 6e02a0f84dbb · 2016-01-15T10:29:09.000+08:00
diff --git a/README.md b/README.md
@@ -36,7 +36,7 @@ $ mv dict.utf8.xdb /etc/scws
 
 # 安装httpscws
 $ cd httpscws
-$ cmake .
+$ cmake . -DCMAKE_INSTALL_PREFIX=/usr/local/httpscws
 $ make
 $ make install
 ```
