Add gitlab-ci.yml

.gitlab-ci.yml

+image: elixir:1.4
+
+services:
+  - postgres:9.6.2
+
+variables:
+  POSTGRES_DB: pleroma_test
+  POSTGRES_USER: pleroma
+  POSTGRES_PASSWORD: pleroma
+
+stages:
+  - test
+
+before_script:
+  - mix local.hex –force
+  - mix local.rebar –force
+  - mix deps.get
+  - MIX_ENV=test mix ecto.create
+  - MIX_ENV=test mix ecto.migrate
+
+unit-testing:
+  stage: test
+  script:
+    - MIX_ENV=test mix test
+
+tags: - elixir 
\ No newline at end of file