Take task-level options as default in target-level
http://gruntjs.com/api/inside-tasks#this.options

```js
webfont: {
  options:{
    engine:'node'
  },
  production: {
    src: 'icons/*.svg',
    dest: 'build/fonts',
    options: {
      htmlDemo: 'false'
    }
  },
  demo: {
    src: 'icons/*.svg',
    dest: 'build/fonts',
    options: {
      htmlDemo: 'true'
    }
  }
}
```
Merge branch 'master' of https://github.com/roadmanfong/grunt-webfont