Mid-position Mixin ignored

The following `Draggable` mixin works:

```js
rml`
  <div class="container" onmouseover="${hov}" ...${Draggable()} >
`;
```

However, it gets ignored when interpolated attributes (like `foo="${bar}"`) are placed after it:

```js
rml`
  <div class="container" ...${Draggable()} foo="${bar}">
`;
```

Check regexes and the logic in the parser