Display build errors in Travis

Travis does not keep state when a build is done, it just reports the final outcome, keeping the log. This means that anything that is not in the output of the build is lost. Having a build fail with only the indication that e.g. `phpcs` failed is not helpful. This PR changes the build so that the output of the tools can be seen in the build log, providing the valuable feedback.

Furthermore a minor improvement has been made on the phplint section, executing it in parallel can help by large changesets.