Add hack to reset classes in tj-form-group directive.

The transclude seems to copy classes onto the new root form-group div.
This leads to issues when setting something like `input-lg` on an
`<input>` in a `tj-form-group`.  Reset it to just have a `form-group`
class.
Add simple alert directive to wrap Bootstrap's alert.
Add style for spinner overlay.
Rebuild dist.