train generator doesn't refresh its images

[galsh17]

Hi,
it seems that there is a bug in the train generator ( PitsSequence ) that causes it to load some images at the first time and then yield only them. I think this is caused by the wrong "on_epoch_start" method - the fit_generator method expects this method to be named "on_epoch_end".

[mpkuse]

keras might have updated since this code was written? Anyways, please send a PR i will accept it.