title: zoom_start option does not work without a location in folium
body: <p>Very simple question here.
  I want to display a world map using python's folium library.
  Here is the code I run to do so:</p>
  <pre><code>import folium
  
  m = folium.Map(height=1000, width=1000, zoom_start=2)
  m.save(&quot;folium_1000_1000_map.html&quot;)
  </code></pre>
  <p>I then open the saved <em>folium_1000_1000_map.html</em> in my browser (firefox), and here is the result:
  <a href="https://i.stack.imgur.com/R9zbz.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/R9zbz.png" alt="enter image description here" /></a></p>
  <p>The zoom_start option does not seem to work.
  I would like the map to display like the next screenshot without having to click on the + button to zoom in once, like I have to at the moment.
  <a href="https://i.stack.imgur.com/X1Rtz.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/X1Rtz.png" alt="enter image description here" /></a></p>
  <p>I have tried to open the <em>folium_1000_1000_map.html</em> in chrome, it does not change anything. The <em>zoom_start</em> option seems to only work when a <em>location</em> parameter is specified, but this is not specified in folium doc. Any idea on how to work around this issue ? Thank you</p>