Remove bluebird dependency, didNot fixes

1. Removed bluebird dependency.
2. Now, we is handling errors in `will[Action]` method. 

*Store:*
``` javascript
willSignIn: function (args) {
  if (!args.email) {
    throw new Error('Email required!');
  }
}
didNotSignIn: function (error) {
  this.update('error', error.message)
} 
```

*Component:*
``` javascript
mixins: [Exim.connect(store, 'error')]
render: function () {
  error = this.state.error;
}
```