fix(events): a few tweaks

demos/native/index.ts

@@ -25,12 +25,21 @@ class MyApp {
 
     console.log('Events', events);
 
-    events.subscribe('user:created', (user) => {
+    let handler = (user) => {
       console.log('User created', user);
       return {
         what: 'what'
       }
-    })
+    }
+    let handler2 = (user) => {
+      console.log('2User created', user);
+      return {
+        things: 'yes'
+      }
+    }
+
+    events.subscribe('user:created', handler);
+    events.subscribe('user:created', handler2);
 
     setInterval(() => {
       var results = events.publish('user:created', {

ionic/util/events.ts

@@ -27,7 +27,7 @@ export class Events {
   }
 
   /**
-   * Unsubscribe the given handler from the given topic. Your handler will
+   * Unsubscribe from the given topic. Your handler will
    * no longer receive events published to this topic.
    *
    * @param topic the topic to unsubscribe from
@@ -38,12 +38,25 @@ export class Events {
   unsubscribe(topic, handler) {
     let t = this.channels[topic];
     if(!t) {
+      // Wasn't found, wasn't removed
       return false;
     }
 
+    if(!handler) {
+      // Remove all handlers for this topic
+      delete this.channels[topic];
+      return true;
+    }
+
+    // We need to find and remove a specific handler
     let i = t.indexOf(handler);
 
-    t.splice(t.indexOf(handler), 1);
+    if(i < 0) {
+      // Wasn't found, wasn't removed
+      return false;
+    }
+
+    t.splice(i, 1);
 
     // If the channel is empty now, remove it from the channel map
     if(!t.length) {