Tweak build instruction content

docs/build-instructions/linux.md

@@ -1,10 +1,8 @@
 # Linux
 
-## Instructions
-
 Ubuntu LTS 12.04 64-bit is the recommended platform.
 
-#### Requirements
+## Requirements
 
   * OS with 64-bit architecture
   * [node.js](http://nodejs.org/download/) v0.10.x
@@ -12,7 +10,7 @@ Ubuntu LTS 12.04 64-bit is the recommended platform.
   * libgnome-keyring-dev `sudo apt-get install libgnome-keyring-dev`
   * `npm config set python /usr/bin/python2 -g` to ensure that gyp uses Python 2
 
-#### Instructions
+## Instructions
 
   ```sh
   git clone https://github.com/atom/atom

docs/build-instructions/os-x.md

@@ -1,14 +1,12 @@
 # OS X
 
-## Instructions
-
-#### Requirements
+## Requirements
 
   * OS X 10.8 or later
   * [node.js](http://nodejs.org/download/) v0.10.x
   * Command Line Tools for [Xcode](https://developer.apple.com/xcode/downloads/) (run `xcode-select --install` to install)
 
-#### Instructions
+## Instructions
 
   ```sh
   git clone https://github.com/atom/atom

docs/build-instructions/windows.md

@@ -1,8 +1,6 @@
 # Windows
 
-## Instructions
-
-#### Requirements
+## Requirements
 
   * Windows 7 or later
   * [Visual C++ 2010 SP1 Express](http://www.visualstudio.com/en-us/downloads/download-visual-studio-vs#DownloadFamilies_4)
@@ -14,7 +12,7 @@
   * Add `C:\Python27;C:\Program Files\nodejs;C:\Users\<user>\github\atom\node_modules\`
     to your PATH
 
-#### Instructions
+## Instructions
 
   ```bat
   cd C:\Users\<user>\github