Global template object support

In a `module.wrapper = false`,
Cannot access compiled template.

I tried to define a global variable.

Example:

config.coffee
```coffeescript
  plugins:
    handlebars:
      namespace: 'JST'
```

templates/sample.hbs
```html
<p>{{name}}</p>
```

some js
```javascript
JST['sample']({ name: 'youkai' })
```