disable gym subpackages in setup.py (#661)

* disable gym subpackages in setup.py

* include gym[atari] in test requirements

* gym[atari] -> atari-py in test requirements

setup.py

@@ -10,7 +10,8 @@ if sys.version_info.major != 3:
 extras = {
     'test': [
         'filelock',
-        'pytest'
+        'pytest',
+        'atari-py'
     ],
     'bullet': [
         'pybullet',
@@ -27,7 +28,7 @@ setup(name='baselines',
       packages=[package for package in find_packages()
                 if package.startswith('baselines')],
       install_requires=[
-          'gym[mujoco,atari,classic_control,robotics]',
+          'gym',
           'scipy',
           'tqdm',
           'joblib',