Add Java 1.6 support

[degerlac]

I know it is hard to believe but I have a WebSphere system that is using Java 1.6 JDK. I would like to use your library without having to fork it. It just needs 3 little changes to compile it with 1.6. Would you consider making these changes and releasing a new version?

Changes:
SpELAssertValidator

Line 64:
    from: private List<Method> functions = new LinkedList<>();
      to: private List<Method> functions = new LinkedList<Method>();

Line 130:
   from: Set<String> names = new HashSet<>(functions.size());
     to: Set<String> names = new HashSet<String>(functions.size());

ReflectionUtils
Line 41

 from: List<Method> staticMethods = new ArrayList<>(allMethods.length);
   to: List<Method> staticMethods = new ArrayList<Method>(allMethods.length);