It should be possible to load/save to pathlib.Path objects, not only str

[alexvicegrab]

Currently when loading/saving to/from pathlib.Path objects:

from pathlib import Path
from omegaconf import OmegaConf

filepath = Path("some_path/some_file.yml")

OmegaConf.load(filepath)
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-4-431f5acec30d> in <module>
----> 1 OmegaConf.load(filepath)

~/anaconda3/envs/nsim-cai-cpu/lib/python3.7/site-packages/omegaconf/omegaconf.py in load(file_)
     60             with io.open(os.path.abspath(file_), "r", encoding="utf-8") as f:
     61                 return OmegaConf.create(yaml.load(f, Loader=get_yaml_loader()))
---> 62         elif getattr(file_, "read"):
     63             return OmegaConf.create(yaml.load(file_, Loader=get_yaml_loader()))
     64         else:

AttributeError: 'PosixPath' object has no attribute 'read'