Update README.md

Amine Mouafik · Amine Mouafik · commit 9524cc222549 · 2014-12-13T00:24:48.000+07:00
diff --git a/README.md b/README.md
@@ -4,7 +4,7 @@
 
 ## Installation
 
-`npm install -s authorize-net`
+    $ npm install -s authorize-net
 
 ## Usage
 
