Implement /ready and basic objective mechanics

src/main/java/gg/malloc/defense/commands/PlayerReadyCommand.java

@@ -0,0 +1,33 @@
+package gg.malloc.defense.commands;
+
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandExecutor;
+import org.bukkit.command.CommandSender;
+import org.bukkit.entity.Player;
+
+import gg.malloc.defense.engine.GameRunner;
+
+import gg.malloc.defense.Plugin;
+
+public class PlayerReadyCommand implements CommandExecutor {
+  Plugin m_plugin;
+
+  public PlayerReadyCommand(Plugin plugin) {
+    m_plugin = plugin;
+  }
+
+  @Override
+  public boolean onCommand(CommandSender sender, Command command, String s, String[] args) {
+    if (sender instanceof Player) {
+      Player player = (Player)sender;
+      GameRunner runner = m_plugin.getRunnerForWorld(player.getLocation().getWorld());
+      runner.addPlayer(player);
+      runner.togglePlayerReady(player);
+      return true;
+    } else {
+      sender.sendMessage("You must be a player to use this command.");
+      return false;
+    }
+  }
+}
+