Revert "Add .gitlab-ci.yml"

This reverts commit 9938ff7f.
There was an attempt to bring CI to this repo, but it failed.
To make sure no problem will exist to CI runner before this gets solved,
revert the configuration: this should stop CI.

.gitlab-ci.yml

-# This file is a template, and might need editing before it works on your project.
-# Official language image. Look for the different tagged releases at:
-# https://hub.docker.com/r/library/rust/tags/
-image: "rust:latest"
-
-# Optional: Pick zero or more services to be used on all builds.
-# Only needed when using a docker container to run your tests in.
-# Check out: http://docs.gitlab.com/ce/ci/docker/using_docker_images.html#what-is-a-service
-#services:
-#  - mysql:latest
-#  - redis:latest
-#  - postgres:latest
-
-# Optional: Install a C compiler, cmake and git into the container.
-# You will often need this when you (or any of your dependencies) depends on C code.
-#before_script:
-#- apt-get update -yqq
-#- apt-get install -yqq --no-install-recommends build-essential
-
-# Use cargo to test the project
-test:cargo:
-  script:
-  - rustc --version && cargo --version      # Print version info for debugging
-  - cargo test --lib --verbose # only test lib (unit) tests as the other need to be root