'select multiple' values not selected in api browser

I believe that the issue is in the select_multiple templates.

I changed the '==' to 'in' and that seemed to fix it. 

```
<option value="{{ select.value }}" {% if select.value == field.value %}selected{% endif %}>{{ select.display_text }}</option>
```

```
<option value="{{ select.value }}" {% if select.value in field.value %}selected{% endif %}>{{ select.display_text }}</option>
```
