title: Truncate a floating point number without rounding up
body: <p>I have a floating point number that I want to truncate to 3 places but I don't want to round up. </p>
  
  <p>For example, convert <code>1.0155555555555555</code> to <code>1.015</code> (not <code>1.016</code>).</p>
  
  <p>How would I go about doing this in Ruby?</p>