Fixes "is_assoc bug"
Fixes "is_assoc bug"

Fixes the bug which prevent calling to `is_assoc` method by declaring this method as static.

-- error without the fix:
```Runtime Notice: Non-static method krumo::is_assoc() should not be called statically in /home/some-user/***/vendor/oodle/krumo/class.krumo.php line 1047"```
scottchiefbaker/krumo,bolt/dumper,mmucklo/krumo,bolt/dumper,scottchiefbaker/krumo,mmucklo/krumo