Enable starting and stopping ray with "ray start" and "ray stop". (#628)

* Install start_ray and stop_ray scripts in setup.py.

* Update documentation.

* Fix docker tests.

* Implement stop_ray script in python.

* Fix linting.

python/setup.py

@@ -65,11 +65,13 @@ setup(name="ray",
       distclass=BinaryDistribution,
       install_requires=["numpy",
                         "funcsigs",
+                        "click",
                         "colorama",
                         "psutil",
                         "redis",
                         "cloudpickle >= 0.2.2",
                         "flatbuffers"],
+      entry_points={"console_scripts": ["ray=ray.scripts.scripts:main"]},
       include_package_data=True,
       zip_safe=False,
       license="Apache 2.0")