Merge branch 'mggmuggins/ci' into 'master'

Add Gitlab CI

See merge request !140

.gitlab-ci.yml

+image: "rust:latest"
+
+before_script:
+    - rustup toolchain add nightly
+    - rustup target add x86_64-unknown-redox --toolchain nightly
+    - rustup show      # Print version info for debugging
+
+build:linux:
+    script:
+        - make all
+
+#build:redox:
+#    script:
+#        - make all
+
+test:linux:
+    script:
+        - make test
+
+fmt:
+    script:
+        - ./fmt.sh -- --write-mode=diff
+
+# TODO: Set up a docker image with a redox vm that would allow to
+#   run things like tests under redox
\ No newline at end of file