title: How to develop rails app for shopify with ScriptTags
body: <p>I have a shopify app deployed in Heroku, developed in Rails. 
  I need call a javascript function from any shopify store's frontend.
  I've read this article ( <a href="http://www.shopify.com/technology/3033852-shopify-api-update-scripttags-javascript-insertion" rel="nofollow">http://www.shopify.com/technology/3033852-shopify-api-update-scripttags-javascript-insertion</a> ), but I don't understand it... </p>
  
  <p>Where do I have to put this code: </p>
  
  <pre><code>HTTP POST http://their-shop.myshopify.com/admin/scripttags
  
    &lt;?xml version="1.0" encoding="UTF-8"?&gt;
    &lt;script-tag&gt;
      &lt;src&gt;http://example.com/your-awesome-script.js&lt;/src&gt;
      &lt;event&gt;onload&lt;/event&gt;
    &lt;/script-tag&gt;
  </code></pre>
  
  <p>What should be the src tag (for my deployed rails app),
  and where should I put the javascript call function? </p>