Test python setup.py install using Travis-CI

For continuous integration, it’s important to test the traditional package install

pip install .

along with the more commonly used in situ pip development mode

pip install -e .

Here’s an example .travis.yml installing from extras_requires while installing the package without pip development mode.

language: python
group: travis_latest

install: pip install .[tests]

script:
- cd $HOME
- pytest $TRAVIS_BUILD_DIR

$TRAVIS_BUILD_DIR is a Travis-CI default environment variable