Added summary README

README.md

+#### (experimental) Argo integration testing
+
+This small repository contains the minimal code necessary to run
+integration tests across the argo stack, using various applications.
+
+It leverages the argopkgs repo, but overrides some sources in it with
+their master branch counterparts. see file `default.nix` for details.
+
+The file `./integration.sh` is provided as a convenience and should be
+all that is necessary to run these tests on a nix-enabled machine.
+
+The real intended usage is to override some of the source with a WIP version,
+as part of development or continuous integration. This gitlab CI snippets shows
+how to do this on a nix-enabled runner:
+
+```{.yml}
+integration.test:
+  stage: test
+  script:
+    - BUILD=$PWD
+    - cd `mktemp -d`
+    - git clone https://xgitlab.cels.anl.gov/argo/argotest.git
+    - cd argotest
+    - nix-shell -A test --run ./integration.hs --arg nrm-src $BUILD
+  except:
+    - /^wip\/.*/
+    - /^WIP\/.*/
+  tags:
+    - integration
+```