Update build requirements

README.md

@@ -8,8 +8,7 @@ Atom is designed to be customizable, but also usable without needing to edit a c
 
 Atom is modern, approachable, and hackable to the core.
 
-Visit [atom.io](http://atom.io)
-to learn more.
+Visit [atom.io](http://atom.io) to learn more.
 
 ## Installing
 
@@ -19,11 +18,45 @@ Atom will automatically update when a new release is available.
 
 ## Building
 
-```sh
-git clone git@github.com:atom/atom.git
-cd atom
-script/build # Creates application at /Applications/Atom.app
-```
+
+**OS X Requirements**
+  * OS X 10.8 or later
+  * [node.js](http://nodejs.org/)
+  * Command Line Tools for [Xcode](https://developer.apple.com/xcode/downloads/) (Run `xcode-select --install`)
+
+  ```sh
+  git clone git@github.com:atom/atom.git
+  cd atom
+  script/build # Creates application at /Applications/Atom.app
+  ```
+
+**Linux Requirements**
+  * Ubuntu LTS 12.04 64-bit is the recommended platform
+  * [node.js](http://nodejs.org/)
+  * `sudo apt-get install libgnome-keyring-dev`
+
+  ```sh
+  git clone git@github.com:atom/atom.git
+  cd atom
+  script/build # Creates application at /tmp/atom-build/Atom
+  sudo script/grunt install # Installs command to /usr/local/bin/atom
+  ```
+
+**Windows Requirements**
+  * Windows 7 or later
+  * [Visual C++ 2010 Express][http://www.microsoft.com/visualstudio/eng/products/visual-studio-2010-express]
+  * [node.js - 32bit][http://nodejs.org/]
+  * [Python 2.7.x][ http://www.python.org/download/]
+  * [GitHub for Windows][http://windows.github.com/]
+  * Clone [atom/atom][https://github.com/atom/atom/] to `C:\Users\<user>\github\atom\`
+  * Add `C:\Python27;C:\Program Files\nodejs;C:\Users\<user>\github\atom\node_modules\`
+    to your PATH
+  * Open the Windows GitHub shell
+
+  ```bat
+  cd C:\Users\<user>\github\atom
+  script/build
+  ```
 
 ## Developing
 Check out the [guides](https://atom.io/docs/latest) and the [API reference](atom.io/docs/api).