new test to showcase onChange bug when triggered via 'edit'

[thanpolas]

There is a bug and an inconsistency on the data object that is passed as parameter on the callback of the onChange event.

I have written this test to illustrate the issues. It is triggered when changing the contents of the table via the setDataAtCell method, which results in triggering an onChange event with the sourceType of edit.

The _bug_ is that no previous value is defined, the array index 2 should contain the previous value of the cell before it was changed. The value of that index is undefined, which apparently is a bug.

The _inconsistency_ is on the col field, or array index 1. When the event is triggered with the setDataAtCell method (source type) the value of the col is its numeric representation.

When the event is triggered by the user editing on the table (source populateFromArray) then the col has the value that was defined in the data as key.

e.g.

var sampleData = [{
  col1: 'a',
  col2: 'b',
  col3: 'c'
}];

$container.handsontable({
  data: sampleData,
  onChange: function (e, source) {
    // Assume we edit Row 0, Col 0
    //
    // When source == edit, then:
    e.shift() == [0, 0, undefined, 'test'];

    // when source == populateFromArray
    e.shift() == [0, 'col1', 'a', 'test'];        
  }
});

[warpech]

Sorry for long wait, finally I put myself together to merge your pull request and fix this. Fixed from version 0.8.11

See the release notes for 0.8.11 for more information about the implications.

[thanpolas]

Never too late :) thanks