detectron infer.py error and few import errors (python 3 related)

[pjspillai]

### Error for the function below
assert isinstance(cfg_to_load, (file, basestring)),
NameError: name 'file' is not defined

def load_cfg(cfg_to_load):
    """Wrapper around yaml.load used for maintaining backward compatibility"""
    assert isinstance(cfg_to_load, (file, basestring)), \
        'Expected {} or {} got {}'.format(file, basestring, type(cfg_to_load))
    if isinstance(cfg_to_load, file):
        cfg_to_load = ''.join(cfg_to_load.readlines())
    if isinstance(cfg_to_load, basestring):
        for old_module, new_module in iteritems(_RENAMED_MODULES):
            # yaml object encoding: !!python/object/new:<module>.<object>
            old_module, new_module = 'new:' + old_module, 'new:' + new_module
            cfg_to_load = cfg_to_load.replace(old_module, new_module)
    return yaml.load(cfg_to_load)

### Also, I am getting a few other import errors:
import cPickle as pickle
import Queue
import urllib2

I modified the scripts to correct these for now

I am using Python 3.6.4 (within Anaconda)

[gadcam]

See #85 & #110