bootstrap-CDN.php

function theme_styles() {

	wp_enqueue_style( 'bootstrap_css', 'https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap-theme.min.css' );
	wp_enqueue_style( 'main_css', get_template_directory_uri() . '/style.css' );

}

add_action( 'wp_enqueue_scripts', 'theme_styles');

function theme_js() {

	global $wp_scripts;

	wp_enqueue_script( 'bootstrap_js', 'https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js');
	wp_enqueue_script( 'my_custom_js', get_template_directory_uri() . '/js/scripts.js');

}

add_action( 'wp_enqueue_scripts', 'theme_js');