Fix await issues. At the moment Jedi is just ignoring await statements.

test/completion/async_.py

@@ -0,0 +1,19 @@
+"""
+Tests for all async use cases.
+
+Currently we're not supporting completion of them, but they should at least not
+raise errors or return strange results.
+"""
+
+
+async def x():
+    await 3
+
+#?
+x()
+
+a = await x()
+#?
+a
+
+