Fixed typo in CLI usage instructions (#74)

Author: tohuw

README.md

@@ -144,7 +144,7 @@ grunt.initConfig({
 
 ### Command Line
 
-Add [postcss-cli]((https://github.com/postcss/postcss-cli))) and PostCSS Sorting to your project:
+Add [postcss-cli](https://github.com/postcss/postcss-cli) and PostCSS Sorting to your project:
 
 ```bash
 npm install postcss-cli postcss-sorting --save-dev