Merge branch 'ci' into 'master'

add CI

See merge request !1

.gitlab-ci.yml

+image: "rust:latest"
+
+before_script:
+  - apt-get update
+  - apt-get install -y protobuf-compiler
+  - rustup component add rustfmt
+  - rustup component add clippy
+  - cargo install cargo-deb
+
+test:
+  script:
+    - cargo fmt -- --check
+    - cargo clippy --all-targets --all-features -- -D warnings
+    - cargo test

README.md

-# igate
+# cats-igate
 
 Reference CATS/FELINET I-gate/digipeater for the Raspberry Pi. Requires an I-Gate board: https://gitlab.scd31.com/cats/pi-hardware