Preprend path

Add lib to the beginning of the search path in test to avoid
loading installed svm_toolkit
Feature Evaluator.MatthewsCorrelationCoefficient

Add an Evaluator calculating the Matthews correlation coefficient.
Add tests for the new evaluator.
Cleanup

Remove verification output
Merge pull request #1 from khellan/master

Evaluator.MatthewsCorrelationCoefficient