title: Angular Material md-select not binding
body: <p>Hello all thanks for reading, i'm having a issue with Angular Material md-select</p>
  
  <p>it doesn't bind with my model. i'm using it to make a form to update data of this model.</p>
  
  <pre><code>&lt;md-input-container class="md-icon md-block" flex ng-controller="ProveedorController" data-ng-init="listaProveedores()"&gt;
  &lt;label&gt;Proveedor&lt;/label&gt;
  &lt;md-select ng-model="detalle.proveedor" required name="proveedores"&gt;
      &lt;md-option ng-value="proveedor" ng-repeat="proveedor in proveedores"&gt;{{proveedor.nombreProveedor}}&lt;/md-option&gt;
  &lt;/md-select&gt;
  </code></pre>
  
  <p></p>
  
  <p>i've tried to use <code>ng-selected</code> but it bind another object that doesn't fit with the original of the model.</p>
  
  <p>any idea what i'm doing wrong?</p>