Create dialogs from Meteor Templates

I've added a method `bootbox.templateDialog(options)` which lets you create modals from meteor templates. I think it would be a great addition to the bootbox package.

I'm open to suggestions on a better api for the new functionality: what do you think of wrapping bootbox.dialog instead of adding a new api call, like so:

    var div = document.createElement("div");
    UI.insert(UI.renderWithData(options.template, options.data), div);
    options.message = div;

Hope this is helpful :)