Add gridObjectTestUtils.

[amyboyd]

Before:

var gridTestUtils = require('lib/gridTestUtils.spec.js');
gridTestUtils.expectHeaderColumnCount('users-table', 6);
gridTestUtils.expectHeaderCellValueMatch('users-table', 0, 'ID');
gridTestUtils.expectHeaderCellValueMatch('users-table', 1, 'Name');
gridTestUtils.expectHeaderCellValueMatch('users-table', 2, 'Email');

After:

var GridObjectTest = require('lib/gridObjectTestUtils.spec.js');
var usersGrid = new GridObjectTest('users-table');
usersGrid.expectHeaderColumnCount(6);
usersGrid.expectHeaderCellValueMatch(0, 'ID');
usersGrid.expectHeaderCellValueMatch(1, 'Name');
usersGrid.expectHeaderCellValueMatch(2, 'Email');

[amyboyd]

Sorry for closing -- thought there was a bug in this -- it was actually a bug in my real tests!

[PaulL1]

That's really elegant. And it looks like it's backwards compatible? (i.e. we can choose to change the existing tests or not change them?)

[amyboyd]

@PaulL1 Yep, it's fully backwards compatible. Thanks for the merge. :)

[PaulL1]

Further, I've just updated the 101 and 102 tutorials to use this format. I noted that @c0bra (I think) has needed to use promises to deal with Firefox, and that code relies on the return value from some of the functions. I updated the object to cascade the return value from each function, which seems to allow that code to keep working as well.