Travis is getting slower and was already hard to debug. This commit:
- moves from travis to Circle-CI
- has a ci-scripts/README.md which explains what is contained there
- puts all build and CI scripts into "ci_scripts" directory
- allows to run full ci runs locally
- trims down the base Docker image where tests/docs/wheels are run from 4.4GB to 1.7GB
- fixes#628
Using circle-ci also means that we can probably integrate Mac-OS build steps more easily.
I am sure that my initial circle-ci config (helped by kind hints from @dignifiedquire ) can be improved.
