Add a horizontal form validation example (check double label classes)

Created by: caiquecastro

The validation feedback for errors (.has-danger) has not been applied to the col-form.label.

<div class="form-group has-danger">
    <label for="name" class="col-form-label">Name</label>
    <input type="text" id="name" name="name" class="form-control">
    <span class="help-block">The name field is required.</span>
</div>