Start dropping missiles when there's already 150 or more on screen

Browsers can't keep up beyond this. I'm betting beyond this point, people will
prefer to lose out on some of the accuracy rather than have the game crawl to a
halt and crank their CPU fan.

src/controller/detonation.js

@@ -21,6 +21,7 @@ GlobalThermonuclearWar.Controller.Detonation = Marionette.Controller.extend({
       latitude: missile.get('target')[0],
       longitude: missile.get('target')[1]
     });
+    this.missiles.remove(missile);
   },
 
   showExplosion: function(explosion) {

src/controller/multiplayer.js

@@ -35,7 +35,9 @@ GlobalThermonuclearWar.Controller.Multiplayer = Marionette.Controller.extend({
   },
 
   receiveMissile: function(rawMissileData) {
-    this.missiles.push(new GlobalThermonuclearWar.Model.Missile(rawMissileData));
+    if (this.missiles.length < 150 ) {
+      this.missiles.push(new GlobalThermonuclearWar.Model.Missile(rawMissileData));
+    }
   },
 
   registerLocation: function(player) {