title: Batch modify text files
body: <p>I have a million markdown files spread across several sub-directories files with different titles where I want to change:</p>
  
  <p><code># A Markdown title</code></p>
  
  <p>to</p>
  
  <pre><code>---
  title: "A Markdown title"
  ---
  </code></pre>
  
  <p>…while keeping the rest of the file intact. Any ideas? OS X solutions prefered.</p>