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"```
fixes typing bug(unneccecary "a" char)

fixes @scottchiefbaker at line 813
Merge pull request #8 from GoDisco/master

Fixes "is_assoc bug"