convert.py problems and no detections

Hi. 
I'm using Tensorflow 2.0.0 version and I had some problems with convert.py
At every line with `np.ndarray(shape=(1,), dtype='int32') #buffer=weights_file.read(4)` I obtained the following error:
`TypeError: buffer is too small for requested array`.
So I removed the buffer option in every nd.array line and it worked.
Now if I run demo.py I have no detections. 
