code: public Object call(Collection coll, Closure c) throws IOException {
          StreamingJsonDelegate.writeCollectionWithClosure(writer, coll, c);
  
          return null;
      }
docs: A collection and closure passed to a JSON builder will create a root JSON array applying
  the closure to each object in the collection
  <p>
  Example:
  <pre class="groovyTestCase">
  class Author {
  String name
  }
  def authors = [new Author (name: "Guillaume"), new Author (name: "Jochen"), new Author (name: "Paul")]
  
  new StringWriter().with { w ->
  def json = new groovy.json.StreamingJsonBuilder(w)
  json authors, { Author author ->
  name author.name
  }
  
  assert w.toString() == '[{"name":"Guillaume"},{"name":"Jochen"},{"name":"Paul"}]'
  }
  </pre>
  @param coll a collection
  @param c a closure used to convert the objects of coll