Support more than 100 comments

[gregwebs]

We perform a single non-paginated API call that returns 100 comments. For a doc with more than 100 comments, not all will be upgraded. There are other examples in the code base of performing paginated API calls.

Very few docs have more than 100 comments. However, I came across one which does. If the API supported filtering out resolved comments, I think this would almost never happen.