title: Load all relationships for a model
body: <p>Usually to eager load a relationship I would do something like this:</p>
  
  <p><code>Model::with('foo', 'bar', 'baz')...</code></p>
  
  <p>A solution might be to set <code>$with = ['foo','bar','baz']</code> however that will always load these three relations whenever I call <code>Model</code></p>
  
  <p>Is it possible to do something like this: <code>Model::with('*')</code>?</p>