See http://arevico.com/make-github-gists-more-responsive for information on how to use this gist

responsive-gists.scss

/**
 * The following code will make a github embedded gists reponsive
 * The gist will be 100% in width width, and scroll if a line is to long
 * if you want wrapping, uncomment the wrapping section
 * Do note that identation may be butcherd tough
 */
.gist{
  
   width:100%;
   
   & table{
	table-layout: fixed;
  }

  & td.js-line-number{
	// We need an explicit width for the other column to be auto
	width: 50px; 
		text-align: center;
	}
 
  
  /*
  // Uncomment this scetion to enable wrapping and disable horizontal scrolling
  & .blob-code-inner{
	 white-space: pre-wrap; 
	 whites-space: wrap;
	 word-wrap:break-word;
 } */
}

i tried this but for some reason it disabled vertical scrolling?