Add tests for elo

* Test for EloCalculator
* Test for ScoreValueCalculator
* Test for ExpectedScoreCaclulator
* Test for TrasformedRatingCalculator
couple things. this should be in the test.

Secondly, since ythere is but one test, consider moving this into instead of using a before filter.

Also consider, making this a bit easier by using methods instead of instance variables.

You only have one thing you care about