Coverage data are now generated by running `gulp unittest` with the `--coverage` argument: unit tests are then executed a single time on Travis. The gulp `coverage` task has been removed and `karma.coverage.conf.ci.js` merged into `karma.conf.ci.js`.
Update documentation with gulp commands (and remove them from `README.md`) and remove unused `config.jshintrc` (oversight from #3256). Delete `thankyou.md` which has been merged into `README.md`.