Add tests for elo

* Test for EloCalculator
* Test for ScoreValueCalculator
* Test for ExpectedScoreCaclulator
* Test for TrasformedRatingCalculator
That's the attitude i'm looking for
![9txcd](https://cloud.githubusercontent.com/assets/755201/5444990/064d411e-847e-11e4-9fd0-581e81a83474.jpg)