Merge branch 'mggmuggins/ci' into 'master'

Gitlab CI

See merge request redox-os/redoxfs!37

.gitlab-ci.yml

+image: "redoxos/redox"
+
+stages:
+    - build
+    - test
+
+before_script:
+    - rustup target add x86_64-unknown-redox --toolchain nightly
+    - rustup show      # Print version info for debugging
+
+cache:
+    paths:
+        - target/
+
+build:linux:cargo:
+    stage: build
+    script: cargo +nightly build --verbose
+
+build:redox:cargo:
+    stage: build
+    script: 
+        - mkdir .cargo
+        - echo -e "[target.x86_64-unknown-redox]\nlinker = \"x86_64-unknown-redox-gcc\"" > .cargo/config
+        - cargo +nightly build --verbose --target x86_64-unknown-redox
+
+test:linux:cargo:
+    stage: test
+    dependencies: 
+        - build:linux:cargo
+    script: cargo +nightly test --verbose
+
+# TODO: Set up a docker image with a redox vm that would allow to
+#   run things like tests under redox