Merge branch 'add-ci' into 'master'

Add basic CI

See merge request famedly/conduit!41

.gitlab-ci.yml

@@ -0,0 +1,13 @@
+image: "rust:latest"
+
+variables:
+  GIT_SUBMODULE_STRATEGY: recursive
+
+before_script:
+  - apt-get update -yqq
+  - apt-get install -yqq --no-install-recommends build-essential libssl-dev pkg-config
+
+test:cargo:
+  script:
+    - rustc --version && cargo --version  # Print version info for debugging
+    - cargo test --workspace --verbose --locked