Merge pull request #400 from Unity-Technologies/docs/python-api

clarify the python docs and learn.py help message

docs/Python-API.md

 
 ## Loading a Unity Environment
 
-Python-side communication happens through `UnityEnvironment` which is located in `python/unityagents`. To load a Unity environment from a built binary file, put the file in the same directory as `unityagents`. In python, run:
-
+Python-side communication happens through `UnityEnvironment` which is located in `python/unityagents`. To load a Unity environment from a built binary file, put the file in the same directory as `unityagents`. If your filename is 3DBall.app, in python, run:
-env = UnityEnvironment(file_name=filename, worker_id=0)
+env = UnityEnvironment(file_name="3DBall", worker_id=0)
-* `file_name` is the name of the environment binary (located in the root directory of the python project). 
+* `file_name` is the name of the environment binary (located in the root directory of the python project).
 * `worker_id` indicates which port to use for communication with the environment. For use in parallel training regimes such as A3C.
 
 ## Interacting with a Unity Environment

python/learn.py

     logger = logging.getLogger("unityagents")
     _USAGE = '''
     Usage:
-      learn (<env>) [options] 
+      learn (<env>) [options]
+      learn --help
-      --help                     Show this message.
       --curriculum=<file>        Curriculum json file for environment [default: None].
       --keep-checkpoints=<n>     How many model checkpoints to keep [default: 5].
       --lesson=<n>               Start learning from this lesson [default: 0].