Fix setup.py

This change
1. Change import order to supress the setuptools warning;
1. Add `zip_safe=False` so that egg installation is disabled.
  By default setuptools assumes torchaudio is zip-safe and `python setup.py install`
  performs egg installation, which causes script module load failure.
  Making `zip_safe=False` force installation to copy the whole directory structure to
  the target directory.
  https://setuptools.readthedocs.io/en/latest/setuptools.html#setting-the-zip-safe-flag

**Warning

```
site-packages/setuptools/distutils_patch.py:25: UserWarning: Distutils was imported before Setuptools. This usage is discouraged and may exhibit undesirable behaviors or errors. Please use Setuptools' objects directly or at least import Setuptools first.
```

** Import failure when installed with `python setup.py install`

```
    import torchaudio
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 656, in _load_unlocked
  File "<frozen importlib._bootstrap>", line 626, in _load_backward_compatible
  File "/torchaudio/envs/master-py3.6/lib/python3.6/site-packages/torchaudio-0.7.0a0+d6831c6-py3.6-linux-x86_64.egg/torchaudio/__init__.py", line 1, in <module>
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 656, in _load_unlocked
  File "<frozen importlib._bootstrap>", line 626, in _load_backward_compatible
  File "/torchaudio/envs/master-py3.6/lib/python3.6/site-packages/torchaudio-0.7.0a0+d6831c6-py3.6-linux-x86_64.egg/torchaudio/extension/__init__.py", line 5, in <module>
  File "/torchaudio/envs/master-py3.6/lib/python3.6/site-packages/torchaudio-0.7.0a0+d6831c6-py3.6-linux-x86_64.egg/torchaudio/extension/extension.py", line 12, in _init_extension
  File "/torchaudio/envs/master-py3.6/lib/python3.6/site-packages/torchaudio-0.7.0a0+d6831c6-py3.6-linux-x86_64.egg/torchaudio/extension/extension.py", line 19, in _init_script_module
  File "/torchaudio/envs/master-py3.6/lib/python3.6/site-packages/torch/_classes.py", line 46, in load_library
    torch.ops.load_library(path)
  File "/torchaudio/envs/master-py3.6/lib/python3.6/site-packages/torch/_ops.py", line 105, in load_library
    ctypes.CDLL(path)
  File "/torchaudio/envs/master-py3.6/lib/python3.6/ctypes/__init__.py", line 348, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: /torchaudio/envs/master-py3.6/lib/python3.6/site-packages/torchaudio-0.7.0a0+d6831c6-py3.6-linux-x86_64.egg/torchaudio/_torchaudio.py
```

Author: mthrok

setup.py

@@ -3,8 +3,8 @@
 import shutil
 import subprocess
 from pathlib import Path
-import distutils.command.clean
 from setuptools import setup, find_packages
+import distutils.command.clean
 
 from build_tools import setup_helpers
 
@@ -85,5 +85,6 @@ def run(self):
     cmdclass={
         'build_ext': setup_helpers.BuildExtension.with_options(no_python_abi_suffix=True)
     },
-    install_requires=[pytorch_package_dep]
+    install_requires=[pytorch_package_dep],
+    zip_safe=False,
 )