Only add typing requirement if python version is <3.5 - #101

I'm having some issues in AWS with this package.

this change is a recommendation from the package maintainers: https://pypi.org/project/typing/

For package maintainers, it is preferred to use typing;python_version<"3.5" if your package requires it to support earlier Python versions. This will avoid shadowing the stdlib typing module when your package is installed via pip install -t . on Python 3.5 or later.

and I also saw this setup change in another project: hardbyte/python-can#452