ProcessExecutor failing

(using osx, python 3.5)

seems to be trouble with using promises and pickle together. Also decorated methods seem to have trouble which means resolvers are often a problem. Adding a comma to args fixes the "Queue is not iterable" error but the second error is much more intricate.

```
ERROR|2016-10-01 01:12:57,673|graphql.execution.executor >> An error occurred while resolving field Query.viewer
Traceback (most recent call last):
File "/Users/ben/.virtualenvs/current/lib/python3.5/site-packages/graphql/execution/executor.py", line 190, in resolve_or_error
return executor.execute(resolve_fn, source, args, context, info)
File "/Users/ben/.virtualenvs/current/lib/python3.5/site-packages/graphql/execution/executors/process.py", line 29, in execute
_process = Process(target=queue_process, args=(self.q))
File "/usr/local/Cellar/python3/3.5.2_1/Frameworks/Python.framework/Versions/3.5/lib/python3.5/multiprocessing/process.py", line 80, in __init__
self._args = tuple(args)
TypeError: 'Queue' object is not iterable
[01/Oct/2016 01:12:57] "POST /graphql? HTTP/1.1" 200 116
Traceback (most recent call last):
File "/usr/local/Cellar/python3/3.5.2_1/Frameworks/Python.framework/Versions/3.5/lib/python3.5/multiprocessing/queues.py", line 241, in _feed
obj = ForkingPickler.dumps(obj)
File "/usr/local/Cellar/python3/3.5.2_1/Frameworks/Python.framework/Versions/3.5/lib/python3.5/multiprocessing/reduction.py", line 51, in dumps
cls(buf, protocol).dump(obj)
TypeError: can't pickle _thread.lock objects
```

从 graphql/execution/executors/process.py 和 graphql/execution/executor.py 中的调用路径开始，然后使用 Python 3.5 在 macOS 上重现该报告。调查 Queue 参数的处理，以及涉及经过装饰的 resolver 和 promises 的 pickling 失败。当 resolver 执行期间不再出现报告中的 Queue 和 _thread.lock 错误时，即表示完成。

由索引模型根据 Issue 内容生成。