adds pause(), resume() and shove()

- pause and resume are usefull to stop processing
the queue and resume later

- shove() places a task in front of the queue

lib/trickle.js

@@ -6,24 +6,45 @@
         this._interval = interval;
         this._requests = [];
         this._lastRun = 0;
+		this._paused = false;
         this._callback = callback;
     };
 
     Trickle.prototype = {
 
         trickle: function (callback) {
-            var self = this;
             this._requests.push(callback);
-            process.nextTick(function () { self._run(); });
-        },
+			this._runNextTick();
+       	},
+
+		shove: function (callback) {
+			this._requests.unshift(callback);
+			this._runNextTick();
+		},
 
         isEmpty: function () {
             return this._requests.length === 0;
         },
 
+		pause: function () {
+			this._paused = true;
+		},
+
+		resume: function () {
+			this._paused = false;
+			this._run();
+		},
+
+		_runNextTick: function () {
+			var self = this;
+            process.nextTick(function () { self._run(); });
+		},
+
         _run: function () {
+			if (this._paused) return;
+
             var now = (new Date()).getTime();
-                    
+
             if (this._isReady()) {
                 this._requests.shift().call();
                 this._lastRun = now;