update setup.py to actually install the package

setup.py

@@ -4,6 +4,7 @@ setup(
     name='gym_minigrid',
     version='0.0.1',
     keywords='memory, environment, agent, rl, openaigym, openai-gym, gym',
+    packages=['gym_minigrid'],
     install_requires=[
         'gym>=0.9.0',
         'numpy>=1.10.0',