Removed spacing around curly braces in CSS rules. Updated tests.

We could maybe add a prettify option down the road.

Juggling methods around to cater for adding styles to (any) store.
Also making return values consistent.

Author: ramonjd

packages/style-engine/class-wp-style-engine-css-rule.php

@@ -110,6 +110,6 @@ public function get_selector() {
 	 * @return string
 	 */
 	public function get_css() {
-		return $this->get_selector() . ' { ' . $this->declarations->get_declarations_string() . ' }';
+		return $this->get_selector() . ' {' . $this->declarations->get_declarations_string() . '}';
 	}
 }