Make templates requirable   

This allows everything within the `templates` array to be required in the js using the name of the file.

```
{
   "name": "foo",
   "scripts": ["index.js"],
   "templates": ["template.html"]
}
```

```
var template = require('template.html')
```

As discussed in [issue 351](https://github.com/component/component/issues/351)