dump results of tests

Because `R CMD check` just gives the last few lines of test runs, it is not that useful. 

This small patch prints the content of the `*.Rout` and `*.Rout.fail` files into the travis log. 

The idea is for some other tool to grab the log and do something useful with it. I'm working on that with the [travis](https://github.com/romainfrancois/travis) package.