ci: Rename .travis/ to ./ci/

ci/README.md

@@ -0,0 +1,8 @@
+## ci scripts
+
+This directory contains scripts for each build step in each build stage.
+
+Currently three stages `lint`, `extended_lint` and `test` are defined. Each stage has its own lifecycle, similar to the
+[Travis CI lifecycle](https://docs.travis-ci.com/user/job-lifecycle#the-job-lifecycle).  Every script in here is named
+and numbered according to which stage and lifecycle step it belongs to.
+