Added PoliteRestClient for optionally rate limiting the requests.
Changed Comment and CommentMapper to return a List of comments for replies, rather than a string.
Added PaginationResult class, and changed Submissions.getSubmissions to return a PaginationResult, to allow paginating the results.
Added an example to get paginated topics.
Merge pull request #86 from aliakhtar/master

Getting paginated submissions, nested replies of comments, and PoliteRestClient for rate limited Rest Requests