Add a continuous integration service

[das7pad]

As chatted in https://github.com/blikenoother/aiourlshortener/pull/4#discussion_r165548200 we want to add a ci service like Travis CI.

Checklist for the CI:

• [ ] style check e.g. lint unused code
  • [ ] set style specs e.g. close to the Google Python Style
• [X] test Shortener creation
• [X] test bitly/goo.gl api calls
• [ ] test bitly/goo.gl api call error handling e.g. use aioresponses to create mocked responses
• [ ] test helper
• [X] scripts to run the test-suite
• [ ] setup a secure environment for the api-keys with travis
• [ ] set supported python versions

[blikenoother]

created new branch #9

[das7pad]

https://github.com/das7pad/aiourlshortener/tree/feature/tests

• I added a Makefile to run tests like make test from the top level directory.
• Tests should run in a fixed environment to get reproduce-able results. The make commands run all in a virtual python environment. I added a make target to generate the requirements make gen-requirements. The test target checks the requirements before running the test-suite (~0.5 seconds).
• Fetch credentials from the terminal environment instead of hard coding templates
• Skip tests in case credentials are missing
• Tests should run independent from others, each test runs in an own event loop
• Basic pipelines for travis and jenkis are added via their config files @blikenoother could you check how we can add the environment variables into the build process of travis?

[das7pad]

bump