Syntax table is incompete

First, thanks so much for the `vue-mode` which I use everyday.

I have a minor issue with `vue-html-mode`. Some characters, for example `:` is set as symbol, this causes a problem when I do a search for symbol from inside section, the search may not catch symbol in section.

For example:
``` html
<template>
<input v-model="aSymbol" /> // do a symbol search for this `aSymbol` here
</template>

<script>
data () {
return {
aSymbol: "Hello" // search for symbol from above won't reach here
}
}

```

The reason is that according to the current `vue-html-mode-syntax-table`, `aSymbol` and `aSymbol:` are different identities. I think `vue-html-mode` needs its own syntax table

Thanks

Start by locating and reading the `vue-html-mode-syntax-table` definition in the mode source. Reproduce the example with `aSymbol` in the `` and `` sections, then verify that symbol search treats the identifier consistently after the syntax-table change.

索引モデルが issue の本文から書いたものです。