bower.json: Add ng-grid dependency

Avoid:

  [12:54:18.773] GET http://localhost:8000/bower_components/ng-grid/ng-grid.css
    [HTTP/1.0 404 File not found 3ms]

I'm not sure which version of ng-grid Gary expected to use in 2d4b0b8f
(Add ng-grid dependencies (pre-3.0), 2014-08-08), but the most recent
tag is 2.0.12, and 2.0.1 came out on 2013-03-06.  I'm going to assume
that ng-grid actually uses semantic versions, and just accept any
version compatible with the 2.0.0 API.