Describe how to use pug with CSS Modules (#95)

* Describe how to use pug with CSS Modules

* Remove unwanted spaces from README

Author: ezhlobo

README.md

@@ -131,7 +131,58 @@ Install [eslint-plugin-react-pug](https://github.com/ezhlobo/eslint-plugin-react
 
 ### CSS Modules
 
-It's not supported well yet.
+Whether you use babel plugin to turn on CSS Modules specifically for JSX (e.g. [babel-plugin-react-css-modules](https://github.com/gajus/babel-plugin-react-css-modules)) or use webpack loader for that to transform styles into key-value object, it's possible to use it with pug.
+
+* With [babel-plugin-react-css-modules](https://github.com/gajus/babel-plugin-react-css-modules) you need to set [`classAttribute`](#classattribute) option to `styleName` value and that's it.
+
+  ```rc
+  {
+    "plugins": [
+      ["transform-react-pug", {
+        "classAttribute": "styleName"
+      }]
+    ]
+  }
+  ```
+
+  ```jsx
+  import './styles.css' // .hello{color:red}
+
+  const withCorrectStyles = pug`
+    div.hello I am a red text
+  `
+  ```
+
+* With webpack loader or other approaches which transform styles into object
+
+  ```jsx
+  import classes from './styles.css' // .hello{color:green}
+
+  const withCorrectStyles = pug`
+    div(className=classes.hello) I am a green text
+  `
+  ```
+
+  The developer experience can be improved here by setting [`classAttribute`](#classattribute) option to `styleName` value and adding [babel-plugin-transform-jsx-css-modules](https://github.com/ezhlobo/babel-plugin-transform-jsx-css-modules)
+
+  ```rc
+  {
+    "plugins": [
+      ["transform-react-pug", {
+        "classAttribute": "styleName"
+      }],
+      "transform-jsx-css-modules"
+    ]
+  }
+  ```
+
+  ```jsx
+  import './styles.css' // .hello{color:green}
+
+  const withCorrectStyles = pug`
+    div.hello I am a green text
+  `
+  ```
 
 ## Install