Alternative syntax for "install" command?

Hyperscript's behaviors are a wonderful thing, but instantiating them on an element always reads a little funny. @dz4k has promoted `I am` as an alias for the `install` command, as in ``. While this reads wonderfully, it could certainly be trouble for the parser. Here are two alternatives to consider:

## "Use"
We're not currently using the keyword `use`, and it seems to fit semantically, as in:

```

```

## Distinct Attribute
Since this is such a DOM-speciic feature, it might work well to separate it into its own attribute -- something like:
```

```
or even
```

```

Thoughts?

Issue には実装ファイルもテストも記載されていません。まず parser のエントリーポイントと DOM の動作処理を特定し、次に提案されている `use` 構文を、属性を分ける代替案と比較してください。合意された構文と、それに対応する parser および動作のカバレッジが揃えば完了です。

索引モデルが issue の本文から書いたものです。