Allow .class on left side of parent/child selectors

[taylor.smock]

node[traffic_calming] { set .traffic_calming }
node.traffic_calming < way[highway] { // Does not work. Expected behavior is to select the way that has the node with the class traffic_calming
        throwError: "Traffic calming in highway (way)";
}
node[traffic_calming] < way[highway] { // Works (example from wiki)
        throwError: "Traffic calming in highway (standard)";
}
way[highway] > node.traffic_calming { // Works, but selects node
        throwError: "Traffic calming in highway (node)";
}