Update charted to 0.4.8 and roll

packages/petitparser/lib/src/lisp/cons.dart

-part of petitparser.lisp;
-
-/// The basic data structure of LISP.
-class Cons {
-
-  /// The head of the cons.
-  dynamic head;
-
-  /// The tail of the cons.
-  dynamic tail;
-
-  /// Constructs a cons.
-  Cons(this.head, this.tail);
-
-  @override
-  bool operator ==(other) {
-    return other is Cons && head == other.head && tail == other.tail;
-  }
-
-  @override
-  int get hashCode => 31 * head.hashCode + tail.hashCode;
-
-  @override
-  String toString() {
-    var buffer = new StringBuffer();
-    buffer.write('(');
-    var current = this;
-    while (current is Cons) {
-      buffer.write(current.head.toString());
-      current = current.tail;
-      if (current != null) {
-        buffer.write(' ');
-      }
-    }
-    if (current != null) {
-      buffer.write('. ');
-      buffer.write(current);
-    }
-    buffer.write(')');
-    return buffer.toString();
-  }
-}