Incorrect data-bind string format breaks in very cryptic way

[tristanls]

If someone writes

< select data-bind="id id, value" >

It will break with unhelpful Uncaught agility.js: unknown argument for getter error message. It would be quite difficult to figure out that the correction is

< select data-bind="value, id id">

[tlack]

Perhaps making the data-bind format look like "value,class=itemClass" rather than "value,class itemClass" would make it easier to visually recognize and detect these errors inside agility.js itself?

[tristanls]

Fixed in #65