error scope for component's slot when in `v-for`

When compiling the example followed, the console will print the error `Error when evaluating the "item.value"`, which is raised by the `slot` directive called in the content linker in `_compile` function (`src/instance/lifecycle`).

``` html
<comp v-for="item in items">
  {{item.value}}
</comp>

<template id="comp">
  <div>
    <slot></slot>
  </div>
</template>
```
