Await is translated to yield

Is the `await` keyword purposely translated to `yield`, or what is the relationship between them for the sake of danger-js?

When I use `await` in my dangerfile (in order to access the promise returned by `git.structuredDiffForFile`), if I get an error, the `await` in my code always appears as a `yield` statement.

For example,
```js
const tables = await asyncFuncThatCallsStructuredDiffForFile(arg);
// Becomes:
var tables = yield asyncFuncThatCallsStructuredDiffForFile(arg);
```

If it's relevant, the error I was looking at is an `SyntaxError: Unexpected identifier` which points to the token directly after the `yield`.

Start by reproducing the behavior in a dangerfile that awaits git.structuredDiffForFile, then inspect how the await expression is transformed before the reported SyntaxError. The issue names no source files or tests; done means establishing whether the await-to-yield translation is expected and addressing the resulting behavior or documenting the relationship.

Written by the indexing model from the issue text.