Add initial support for Travis CI

[misery]

No description provided.

[GitMensch]

@misery: I highly suggest to register for coverity scan and automate the checks via Travis - see https://scan.coverity.com/github

[misery]

@GitMensch
Thanks for the suggestion.
We already registered coverity scan: https://scan.coverity.com/projects/governikus-ausweisapp2

[GitMensch]

@misery This is good. What do you think about adding the badge to the readme?
For example with

[![Coverity Scan Build Status](https://scan.coverity.com/projects/governikus-ausweisapp2/badge.svg)](https://scan.coverity.com/projects/governikus-ausweisapp2)

shows as

[misery]

@GitMensch
Well, I like those badges. But coverity scan is checked carefully and there are some false-positives like these "5 new defects". We do not want to scare people about security issues that do not exist.

[GitMensch]

@misery I see. But if you are investigating these in general and mark false-positives as false-positives + trigger recheck those should go away from the badge and you show to users that you actually do coverity check.