This commit makes a substantial change to the API, changing the CloudEvent class
to accept properties as an object in the constructor. For example:
```js
const CloudEvent = require('cloudevents-sdk');
// all event properties except extensions may be set in the constructor
const event = new CloudEvent({
source: 'http://my.event.source',
type: 'test-event-type'
});
// get and set all properties standard property notation
console.log(event.time); // the event timestamp
event.subject = 'my event subject';
```
Signed-off-by: Lance Ball <lball@redhat.com>
Lance Ball