rearrange redis calls so they are executed in the right order

lib/index.js

@@ -21,10 +21,11 @@ sys.inherits(WheresWaldo, process.EventEmitter)
 
 WheresWaldo.prototype.track = function(user, location) {
   this.emit('track', user, location)
-  return promises.group(
-    this.cleanupOldUserLocation(user),
-    this.setUserLocation(user, location),
-    this.addLocationUser(user, location))
+  var waldo = this
+  return this.cleanupOldUserLocation(user, location).addCallback(function() {
+    waldo.setUserLocation(user, location)
+    waldo.addLocationUser(user, location)
+  })
 }
 
 WheresWaldo.prototype.locate = function(user) {
@@ -60,21 +61,27 @@ WheresWaldo.prototype.key = function() {
   return args.join(":")
 }
 
-WheresWaldo.prototype.cleanupOldUserLocation = function(user) {
+WheresWaldo.prototype.cleanupOldUserLocation = function(user, location) {
   var waldo = this,
         key = this.key(user)
   return this.redis.get(key).addCallback(function(oldLocation) {
-    if(oldLocation)
+    if(oldLocation && oldLocation != location)
       waldo.redis.del(waldo.key(oldLocation, user))
   })
 }
 
 WheresWaldo.prototype.setUserLocation = function(user, location) {
-  var key = this.key(user)
-  return promises.group(this.redis.set(key, location), this.redis.expire(key, this.age))
+  var key = this.key(user),
+    waldo = this
+  return this.redis.set(key, location).addCallback(function() {
+    waldo.redis.expire(key, waldo.age)
+  })
 }
 
 WheresWaldo.prototype.addLocationUser = function(user, location) {
-  var key = this.key(location, user)
-  return promises.group(this.redis.set(key, 1), this.redis.expire(key, this.age))
+  var key = this.key(location, user),
+    waldo = this
+  return this.redis.set(key, 1).addCallback(function() {
+    waldo.redis.expire(key, waldo.age)
+  })
 }