`await` inside async function

The async API doc examples for the 'await' should be inside an async function to work in python asyncio - although the example code is fine it would be clearer/nicer if this was included.

```
async def getBucket():
bucket = cluster.bucket("travel-sample")
await bucket.on_connect()
collection = bucket.default_collection()
```

Reporter: Emily Wisher
E-mail: emily.wisher@couchbase.com