There is no CI to automatically update PyPi

[tompreston]

According to The Hitchiker's Guide, PyPi is the right solution to distribute Python software as it is cross-platform (many Linuxes, macOS and Windows I think).

GitHub supports Travis CI to automatically test and deploy (push to PyPi) software, which is something pifacedigitalio and friends require. With this change, bug fixes and improvements in the form of Pull Requests can reach users without too much intervention.

Tasks include:

• Research Travis CI
• Write CI configuration
• Link project to Travis CI