Adafruit-circuitpython-ds1307

Updated requirements. Thanks demophoon.

To use in CircuitPython, simply install the [Adafruit CircuitPython bundle](https://github.com/adafruit/Adafruit_CircuitPython_Bundle).

To use in CPython, `pip3 install adafruit-circuitpython-ds1307`.

Read the [docs](http://circuitpython.readthedocs.io/projects/ds1307/en/latest/) for info on how to use it.

To use in CircuitPython, simply install the [Adafruit CircuitPython bundle](https://github.com/adafruit/Adafruit_CircuitPython_Bundle).

To use in CPython, `pip3 install adafruit-circuitpython-ds1307`.

Read the [docs](http://circuitpython.readthedocs.io/projects/ds1307/en/latest/) for info on how to use it.

To use in CircuitPython, simply install the [Adafruit CircuitPython bundle](https://github.com/adafruit/Adafruit_CircuitPython_Bundle).

To use in CPython, `pip install adafruit-circuitpython-ds1307`.

Read the [docs](http://circuitpython.readthedocs.io/projects/ds1307/en/latest/) for info on how to use it.

- Added `setup.py`
- Added PyPI release info to `.travis.yml`
- Updated `requirements.txt`
- Added a more comprehensive `.gitignore`

To use in CircuitPython, simply install the [Adafruit CircuitPython bundle](https://github.com/adafruit/Adafruit_CircuitPython_Bundle).

To use in CPython, `pip install adafruit-circuitpython-ds1307`.

Read the [docs](http://circuitpython.readthedocs.io/projects/ds1307/en/latest/) for info on how to use it.

Thanks to sommersoft for the great work!

Added demo.py to examples folder