title: simple regex -- replace underscore with a space
body: <p>Hey, I'm writing my first Rails app, and I'm trying to replace the underscores form an incoming id name with spaces, like this:</p>
  
  <p><strong>before</strong>: test_string</p>
  
  <p><strong>after</strong>:  test string</p>
  
  <p>How can I do this? Sorry if this is a bit of a dumb question, I'm not very familiar with regular expressions...</p>