Added implementation of RatingChange
Added implementation of JudgeProtocol
Added implementation of Hack
Added implementation of ProblemResult
Renamed ProblemResults to ProblemResult
Added implementation of RanklistRow
Added implementation of 'contest.hacks' method
Added implementation of contest.status method
Fixed verdict field (it may be absent)
Added implementation for problemset.recentStatus method
Added implementation of user.rating method
Refactoring: improved implementation of contest.standings method.

Split one kwargs parameter into separate parameters
Added asserts
This function returns list of RanklistRow now as part of dictionary
Improved doc comment
Refactoring: split data retrieving in separate class
Fixed parameter in request
Added support for authorization through private API key and secret