Hook up With Travis CI

[ThomasThelen]

We should be doing automated builds when we push new code and make pull requests. This lets us know if the code coverage decreased (not enough unit tests) or if something broke the package.

We should be automating the testing on both UNIX and macOS-Travis doesn't yet support Windows with R

[ThomasThelen]

The goal is to set up Travis CI, see this for reference. You can also search around GitHub for R libraries and chances are that they do this. You can see a simple examples here and here and a more complex one here

While we're at it we should integrate with codecov (measures how much the code is being tested). A great example of codecov can be found here.

Unfortunately Travis only supports private repositories with the Pro feature, so we'll have to wait until we make this public.