fix import path

[hui-po-wang]

Hi machrisaa,

Thank you for sharing this amazing project.

In test_vgg16.py, test_vgg19.py, and test_vgg19_trainable, I think there are some typos. It seems that tensoflow_vgg should be corrected to tensorflow_vgg, right? Despite changing those typos (I assume they are) and adding sys.path.append("../"), it doesn't match the name of your github project.

So, I made some changes to help those who want to test your project very quickly.

-from tensoflow_vgg import vgg16
-from tensoflow_vgg import utils
+import vgg16
+import utils

[machrisaa]

Thanks for fixing the typo