Request all Tracks with specified offset and limit

Can be filtered by passing non-nil start & end dates

@param offset Page offset.
 @param limit Page limit.
 @param startDate Optional value to filter tracks.
 @param endDate Optional value to filter tracks.
 @param callback Completion handler with RPFeed as a response.
- (void)getTracksWithOffset:(NSUInteger)offset
                      limit:(NSUInteger)limit
                  startDate:(NSDate *)startDate
                    endDate:(NSDate *)endDate
                 completion:(RPAPIEntryCallback)callback;