add .travis.yml file for automatic testing of build process by travis-ci.com
tweak .travis.yml file for parallel build (make -j4)
add the README.md file with travis.com build status
tweak .travis.yml file so that it uses the same commands as suggested by the README for a quick install
tweak .travis.yml file to only use gcc (the clang build fails because the clang compiler runs out of memory while compiling some files)