Minor refactorings and code style changes (#807)

* Made minor changes in some patterns such as removed throws clause where not needed, changed incorrect order of arguments in assertEquals

* Minor refactorings and code style changes. 1) Removed several use of raw types 2) Removed unnecessary throws clauses 3) Used lambda expressions wherever applicable 4) Used apt assertion methods for readability 5) Use of try with resources wherever applicable 6) Corrected incorrect order of assertXXX arguments

* Removed unused import from Promise

* Addressed review comments

* Addressed checkstyle issue

factory-kit/src/test/java/com/iluwatar/factorykit/factorykit/FactoryKitTest.java

@@ -83,7 +83,7 @@ public class FactoryKitTest {
    * @param weapon weapon object which is to be verified
    * @param clazz  expected class of the weapon
    */
-  private void verifyWeapon(Weapon weapon, Class clazz) {
+  private void verifyWeapon(Weapon weapon, Class<?> clazz) {
     assertTrue(clazz.isInstance(weapon), "Weapon must be an object of: " + clazz.getName());
   }
 }