fix(EventEmitter): Update rxjs dependency. Add 'emit' method.

fixes #122

BREAKING CHANGE:

Before:
```js
@output() foo = new EventEmitter();

foo.next();
```

Before:
```js
@output() foo = new EventEmitter();

foo.emit(); // <--
```

lib/events/event-emitter.ts

@@ -1,4 +1,4 @@
-import Subject from '@reactivex/rxjs/dist/es6/Subject';
+import Subject from 'rxjs/Subject';
 
 /**
  * Use by directives and components to emit custom Events. Copied from Angular 2's [EventEmitter](

package.json

@@ -31,7 +31,7 @@
   ],
   "license": "ISC",
   "dependencies": {
-    "@reactivex/rxjs": "5.0.0-alpha.7",
+    "rxjs": "5.0.0-beta.0",
     "reflect-metadata": "^0.1.2"
   },
   "devDependencies": {