Imputing missing values when computing distances
Data imputation on distances is performed only when needed by Distances widget
Sort by predicted values in Predictions widget
Merge pull request #180 from thocevar/tree

Fixed tree tests using multinomial attributes with scikit-learn methods.
Leave the original data intact when imputing values for distance computation.
TestLearners AUC metric.
Merge pull request #177 from marinkaz/distances

Imputing missing values when computing distances.
Restore original order in Predictions widget.
Clean imports.
Hides sort indicator for unsorted ordering in Predictions widget.
Improve code clarity.
Merge pull request #179 from thocevar/predictions

Sort by predicted values in Predictions widget
Binary measures.
Merge pull request #182 from acopar/test-learners-auc

Test learners auc
Supported numpy arrays as inputs for distances. Handling e1, e2 separately. Implemented extension ob basic classes.
Added documentation for Distances.
Merge pull request #181 from nikicc/npmat

Supported numpy arrays as inputs for distances.
Started documentation for the statistics module.