Added better explanation for -g option.

igauravsehrawat · igauravsehrawat · commit 26b4578c8387 · 2017-07-25T10:37:10.000+05:30
diff --git a/README.md b/README.md
@@ -49,7 +49,7 @@ clean-css-cli requires Node.js 4.0+ (tested on Linux, OS X, and Windows)
 ```shell
 npm install clean-css-cli -g
 ```
-Note: Global install is mandatory for CLI purpose.
+Note: Global install via -g option is recommended unless you want to execute the binary via a relative path, i.e. ./node_modules/.bin/cleancss
 
 # Use
 
