Add checkipnb.py script
travis-ci: install ipython; run checkipnb
travis-ci: install cython; run second tutorial
travis-ci: install matplotlib etc. via apt-get for notebook tests
Fix .travis.yml errors with travis-lint
travis-ci: fix formatting error in .travis.yml
travis-ci: fix more formatting error in .travis.yml
travis-ci: move install and script code to separate shell scripts
travis-ci: fix bash script error