More RPG Dice Functions

d30 dice are becoming more popular and some resources are beginning to include tables for them, so I've added a d30 function. I've also added a generic `.rpg()` function which can be used to simulate multiple die rolls using fairly standard notation:

    var yacht = chance.rpg("5d6");
    document.write(yacht.join("|"));
    // Example output: 4|2|1|6|6

Also snuck in an optimization for my earlier array shuffle function. :)