pubsub.unsubscribe without handler reference

SPEC/PUBSUB.md

@@ -51,6 +51,8 @@ A great source of [examples][] can be found in the tests for this API.
 If no `callback` is passed, a [promise][] is returned.
 
 This works like `EventEmitter.removeListener`, as that only the `handler` passed to a `subscribe` call before is removed from listening. The underlying subscription will only be canceled once all listeners for a topic have been removed.
+The other options is to use this method with only `topic` as input, without the need to keep a reference to the `handler` function. 
+This works like `EventEmitter.remoteAllListeners`, removes all listeners from the given topic. 
 
 **Example:**
 
@@ -78,6 +80,25 @@ ipfs.pubsub.subscribe(topic, receiveMsg, (err) => {
 })
 ```
 
+Or removing all listeners: 
+```JavaScript
+const topic = 'fruit-of-the-day'
+const receiveMsg = (msg) => console.log(msg.toString())
+
+ipfs.pubsub.subscribe(topic, receiveMsg, (err) => {
+  if (err) {
+    return console.error(`failed to subscribe to ${topic}`, err)
+  }
+
+  console.log(`subscribed to ${topic}`)
+
+  setTimeout(() => {
+    // Will unsubscribe ALL handlers for the given topic
+    ipfs.pubsub.unsubscribe(topic);
+  }, 1000)
+})
+```
+
 A great source of [examples][] can be found in the tests for this API.
 
 #### `pubsub.publish`

src/pubsub/unsubscribe.js

@@ -57,5 +57,21 @@ module.exports = (createCommon, options) => {
         )
       })
     })
+    it('should subscribe and unsubscribe with no handler', (done) => {
+      const someTopic = getTopic()
+      const handler = (msg) => {}
+      ipfs.pubsub.subscribe(someTopic, handler, (err) => {
+        expect(err).to.not.exist()
+        ipfs.pubsub.unsubscribe(someTopic)
+        setTimeout(() => {
+          // Assert unsubscribe worked
+          ipfs.pubsub.ls((err, topics) => {
+            expect(err).to.not.exist()
+            expect(topics).to.eql([])
+            done()
+          })
+        }, 500)
+      })
+    })
   })
 }