title: Leaflet.js center the map on a group of markers
body: <p>I'm using <code>Leaflet.js</code> and would like some way to centre the map on the markers I have so that all are within the user's view when the page launches. If all the markers are clustered in a small area, I would like the map to zoom down to a level that still displays all of them.</p>
  
  <p>I know google maps has an auto-centre function but how would I go about this with Leaflet.js?</p>