Added first event - instance.new - with documentation on README

Issue play-with-docker#3

Author: mikesir87

README.md

@@ -29,4 +29,13 @@ Clone this repo and run `npm install && npm run build`
 
 ## Development
 
-To make development easier, run `npm install && npm run dev`. All file changes will automatically trigger a Webpack build.
+To make development easier, run `npm install && npm run dev`. All file changes will automatically trigger a Webpack build.
+
+
+## Events
+
+The SDK provides the ability to listen to various events. The events are outlined below
+
+| Event Name         | Arguments       | Description                            |
+|--------------------|-----------------|----------------------------------------|
+| `instance.new`     | instanceDetails | Invoked when a new instance is created |

index.js

@@ -120,6 +120,7 @@ import * as Emitter from 'tiny-emitter';
     } else {
       console.warn('No terms specified, nothing to do.');
     }
+    return this;
   };
 
   // your sdk init function
@@ -160,7 +161,7 @@ import * as Emitter from 'tiny-emitter';
         var i = session.instances[name];
         // Setup empty terms
         i.terms = [];
-        self.instances[name] = i;
+        registerInstance(self, name, i);
       }
       !callback || callback();
     });
@@ -227,14 +228,19 @@ import * as Emitter from 'tiny-emitter';
     }
   };
 
+  function registerInstance(pwd, name, instanceMetadata) {
+    pwd.instances[name] = instanceMetadata;
+    pwd.eventEmitter.emit("instance.new", instanceMetadata);
+  }
+
   pwd.prototype.createInstance = function(callback) {
     var self = this;
     //TODO handle http connection errors
     sendRequest('POST', self.opts.baseUrl + '/sessions/' + this.sessionId + '/instances', {headers:{'Content-type':'application/json'}}, {ImageName: self.opts.ImageName}, function(response) {
       if (response.status == 200) {
         var i = JSON.parse(response.responseText);
         i.terms = [];
-        self.instances[i.name] = i;
+        registerInstance(self, i.name, i);
         callback(undefined, i);
       } else if (response.status == 409) {
         var err = new Error();