Change Row.data to Row.as_void() internally, remove Row._mask property
Remove orphaned routine create_mask from initial MaskedColumn implementation
Deprecate Table._data in favor of explicit Table.as_array()
Use actual array values in Row.as_void (fixes py3 issue as well)
Py3 compatibility for table_helpers
Fix mistake creating data for Row.as_void(), add test
Update the ParamsRow subclass example and include as test