List 3.
Initial average, mode and median implementation.
comment new implementation to have tests green
Add ItemRange.
Add Item.
Add ItemContinuous and ItemDiscrete.
Add Table.
Refactory statistic using Table and Item classes.
Remove comments from Rakefile.
Implement xifi sum to table and itens.
Refactor in type, total calculation and size.
Refactor in ItemContinuous.
Support to Continuous median calculation.
Support to continuous mode calculation.
Implement median prints and refactor print methods.
Apply new syntax in Rakefile.