AC: Update searchJira to allow setting startAt and maxResults

The searchJira function currently hard codes the startAt or maxResults parameters. This pull request makes these parameters customizable in a backwards compatible way. Tests are updated and green.

```js
// old usage:
searchJira(query, fields, cb);

// new usage:
searchJira(query, { fields: fields, startAt: 200, maxResults: 50 }, cb);
```