Make dependencies for Token plugins optional

redis and jwcrypto are not required to use websockify so configure
these as optional requirements for specific features (redis, jwt)
rather than always installing.

setup.py

@@ -31,9 +31,11 @@ setup(name=name,
       include_package_data=True,
       install_requires=[
         'numpy', 'requests',
-        'jwcrypto',
-        'redis',
         ],
+      extras_requires={
+        'redis': ['redis'],
+        'jwt': ['jwcrypto'],
+        },
       zip_safe=False,
       entry_points={
         'console_scripts': [