Enqueue Child CSS to Load After Bootstrap CDN

Adding the dependency should work.

You are not calling your theme styles file correctly though. You need to move your theme-style.css file down to the root folder of the theme itself and name it style.css.

So your function should look as follows:

function my_enqueues() {
    wp_enqueue_style( 'bootstrap-css', '//maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css' );
    wp_enqueue_style( 'theme-css', get_stylesheet_uri(), array( 'bootstrap-css' ) );
}
add_action( 'wp_enqueue_scripts', 'my_enqueues' );

This also fits with the Theme Handbook section on Including CSS & JavaScript.