title: Can't parse a json to a `ProvinceJson` class, with lift-json
body: <p>Scala code:</p>
  
  <pre><code>import net.liftweb.json._
  
  case class Province(id: String, name: String, parentName: Option[String], parentId: Option[String])
  
  case class ProvinceJson(provinceData: List[Province])
  
  object Test extends Application {
    val json = """ {
                 |    "provinceData":
                 |        [
                 |            {
                 |                "name":"hb",
                 |                "parentName":null,
                 |                "parentId":null,
                 |                "id":"450"
                 |            }
                 |        ]
                 |}
                 | """.stripMargin
  
    parse(json).extract[ProvinceJson]
  
  }
  </code></pre>
  
  <p>When I run this code, it reports compilation error:</p>
  
  <pre><code>could not find implicit value for parameter formats: net.liftweb.json.Formats
  parse(json).extract[ProvinceJson]
                      ^
  
  not enough arguments for method extract: (implicit formats: net.liftweb.json.Formats, implicit mf: scala.reflect.Manifest[com.thoughtworks.sfexpress.sf_ws.ProvinceJson])com.thoughtworks.sfexpress.sf_ws.ProvinceJson.
  Unspecified value parameters formats, mf.
  parse(json).extract[ProvinceJson]
                      ^
  </code></pre>
  
  <p>Do I miss anything?</p>