Fix when we decide to "not exit on command error". We were doing this
too late so if the unittests failed the lit tests would not run.
Clean up travis build scripts a little.
Capture STP build output to file and only show its contents if there
is a build failure. This is so the output shown in the TravisCI
web interface is kept small.
Merge pull request #154 from delcypher/travis_script_fixes

Travis clean ups