error scope for fallback content of slot

[TerenceZ]

Compiling the transcluded slot content and fallback content should be with different scope, however, at current 1.0.0 (0.12.0 is compiled properly), these two are compiled with the vm' _scope, which means that the value something as followed will be resolved from the outside world, not from the vm itself.

<template id="abc">
<div>
  <slot>{{something}}</slot>
</div>
</template>