fixing a typo in readme

missing async in function definition in the test examples

README.md

@@ -358,7 +358,7 @@ If we want to test the relationship between our container and the component
we can again construct our own instance and inject it into the tree.

```js
test('counter', () => {
test('counter', async () => {
  let counter = new CounterContainer();
  let tree = render(
    <Provider inject={[counter]}>
@@ -378,7 +378,7 @@ Dependency injection is useful in many ways. Like if we wanted to stub out a
method in our state container we can do that painlessly.

```js
test('counter', () => {
test('counter', async () => {
  let counter = new CounterContainer();
  let inc = stub(counter, 'increment');
  let dec = stub(counter, 'decrement');