removed os from requirements.txt

requirements.txt

 setuptools
 docopt
-os
-argparse
-importlib
-logging
-time
 matplotlib
 numpy
 bob.extension
@@ -13,3 +8,7 @@ bob.io.base
 bob.io.image
 torch >= 0.4.0
 torchvision >= 0.2.0
+argparse
+importlib
+logging
+time