Set zip_safe = False

Currently `setuptools` assumes that torhcaudio is zip safe and performs
egg (zip) installation when `python setup.py install` (or `pip install .`).

Torchaudio checks module (C++ extension) availavility dynamically at runtime,
using importlib, and egg installation does not work well with this. (importlib
cannot find C++ extension with egg installation even though it exists)

An workaround for this is to set zip_safe=False in setup.py and disable egg
installation, so that `python setup.py install` installs uncompressed files
with regular directory structure.

setup.py

@@ -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,
 )