[xray] Integrate worker.py with raylet. (#1810)

* Integrate worker with raylet.

* Begin allowing worker to attach to cluster.

* Fix linting and documentation.

* Fix linting.

* Comment tests back in.

* Fix type of worker command.

* Remove xray python files and tests.

* Fix from rebase.

* Add test.

* Copy over raylet executable.

* Small cleanup.

test/xray_test.py

@@ -0,0 +1,49 @@
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+
+import pytest
+import ray
+
+
+@pytest.fixture
+def ray_start():
+    # Start the Ray processes.
+    ray.init(num_cpus=1, use_raylet=True)
+    yield None
+    # The code after the yield will run as teardown code.
+    ray.worker.cleanup()
+
+
+def test_basic_task_api(ray_start):
+
+    # Test a simple function.
+
+    @ray.remote
+    def f_simple():
+        return 1
+
+    assert ray.get(f_simple.remote()) == 1
+
+    # Test multiple return values.
+
+    @ray.remote(num_return_vals=3)
+    def f_multiple_returns():
+        return 1, 2, 3
+
+    x_id1, x_id2, x_id3 = f_multiple_returns.remote()
+    assert ray.get([x_id1, x_id2, x_id3]) == [1, 2, 3]
+
+    # Test arguments passed by value.
+
+    @ray.remote
+    def f_args_by_value(x):
+        return x
+
+    args = [1, 1.0, "test", b"test", (0, 1), [0, 1], {0: 1}]
+    for arg in args:
+        assert ray.get(f_args_by_value.remote(arg)) == arg
+
+    # Test arguments passed by ID.
+
+    # Test keyword arguments.