Add API docs

[thijstriemstra]

• use tox to test against multiple python versions
• add sphinx api documentation
• enforce pep8 style using flake8

fixes #5

[thijstriemstra]

This is a work in progress @kplindegaard, I'll let you know when it's ready for review.

[kplindegaard]

Looking forward to it. Thanks!

[thijstriemstra]

@kplindegaard I see many methods with a comment before the docstring like this:

    def open(self, bus):
        # type: (int) -> None
        """
        Open a given i2c bus.
        :param bus: i2c bus number (e.g. 0 or 1)
        """
        self.fd = os.open("/dev/i2c-{}".format(bus), os.O_RDWR)
        self.funcs = self._get_funcs()

e.g. # type: (int) -> None. Unfortunately this seems to screw up Sphinx, can I move those below the docstring instead?

[kplindegaard]

Go ahead. Could alternatively be deleted and we could add type hints in the docstring itself.

[thijstriemstra]

Go ahead. Could alternatively be deleted and we could add type hints in the docstring itself.

I'll move them below the docstring and then you can later review them and move it into docstring.

[kplindegaard]

👍

[thijstriemstra]

@kplindegaard this PR should be ready to go.

[thijstriemstra]

ps. i would squash merge this.. and you'll have to enable this repository on readthedocs.

[kplindegaard]

I hid some parts i don't think will be very relevant for the normal user and published the documentation on Read the docs
@thijstriemstra: Thank you for the great job you did!