Update README.md

Improve documentation by adding links to the npm package page,

README.md

@@ -1,16 +1,19 @@
-# postcss-calc [![Build Status](https://travis-ci.org/postcss/postcss-calc.png)](https://travis-ci.org/postcss/postcss-calc)
+# PostCSS Calc [<img src="https://postcss.github.io/postcss/logo.svg" alt="PostCSS" width="90" height="90" align="right">][PostCSS]
 
-> [PostCSS](https://github.com/postcss/postcss) plugin to reduce `calc()`.
+[![NPM Version][npm-img]][npm-url]
+[![Build Status][cli-img]][cli-url]
+[![Support Chat][git-img]][git-url]
 
-This plugin reduce `calc()` references whenever it's possible.
-This can be particularly useful with the [postcss-custom-properties](https://github.com/postcss/postcss-custom-properties) plugin.
+[PostCSS Calc] lets you reduce `calc()` references whenever it's possible. This
+can be particularly useful with the [PostCSS Custom Properties] plugin.
 
-**Note:** When multiple units are mixed together in the same expression, the `calc()` statement is left as is, to fallback to the [w3c calc() feature](http://www.w3.org/TR/css3-values/#calc).
+When multiple units are mixed together in the same expression, the `calc()`
+statement is left as is, to fallback to the [W3C calc() implementation].
 
 ## Installation
 
-```console
-$ npm install postcss-calc
+```bash
+npm install postcss-calc
 ```
 
 ## Usage
@@ -31,7 +34,7 @@ var output = postcss()
   .css
 ```
 
-**Example** (with [postcss-custom-properties](https://github.com/postcss/postcss-custom-properties) enabled as well):
+**Example** (with [PostCSS Custom Properties] enabled as well):
 
 ```js
 // dependencies
@@ -86,7 +89,7 @@ h1 {
 }
 ```
 
-Checkout [tests](src/__tests__/index.js) for more examples.
+Checkout [tests] for more examples.
 
 ### Options
 
@@ -103,7 +106,8 @@ var out = postcss()
 
 #### `preserve` (default: `false`)
 
-Allow you to preserve calc() usage in output so browsers will handle decimal precision themselves.
+Allow you to preserve calc() usage in output so browsers will handle decimal
+precision themselves.
 
 ```js
 var out = postcss()
@@ -157,15 +161,29 @@ div[data-size="calc(3*3)"] {
 
 ## Contributing
 
-Work on a branch, install dev-dependencies, respect coding style & run tests before submitting a bug fix or a feature.
+Work on a branch, install dev-dependencies, respect coding style & run tests
+before submitting a bug fix or a feature.
 
-```console
-$ git clone https://github.com/postcss/postcss-calc.git
-$ git checkout -b patch-1
-$ npm install
-$ npm test
+```bash
+git clone git@github.com:postcss/postcss-calc.git
+git checkout -b patch-1
+npm install
+npm test
 ```
 
 ## [Changelog](CHANGELOG.md)
 
 ## [License](LICENSE)
+
+[cli-img]: https://img.shields.io/travis/postcss/postcss-calc/master.svg
+[cli-url]: https://travis-ci.org/postcss/postcss-calc
+[git-img]: https://img.shields.io/badge/support-chat-blue.svg
+[git-url]: https://gitter.im/postcss/postcss
+[npm-img]: https://img.shields.io/npm/v/postcss-calc.svg
+[npm-url]: https://www.npmjs.com/package/postcss-calc
+
+[PostCSS]: https://github.com/postcss
+[PostCSS Calc]: https://github.com/postcss/postcss-calc
+[PostCSS Custom Properties]: https://github.com/postcss/postcss-custom-properties
+[tests]: src/__tests__/index.js
+[W3C calc() implementation]: https://www.w3.org/TR/css3-values/#calc-notation