sync_batchnorm missing

[deepglugs]

Looks like this file might be missing from source: ```ModuleNotFoundError: No module named 'models.networks.sync_batchnorm'

[nisargshah1999]

This would solve the issue, #2

[EladWarshawsky]

pip install sync_batchnorm
from sync_batchnorm import SynchronizedBatchNorm2d

the install works for me, and the import does as well. Haven't tested it with the actual model yet. I'll let you know.