Enable CI (#2)

Reviewed-on: pierre/GrammalecteClient#2

.drone.yml

@@ -0,0 +1,14 @@
+---
+kind: pipeline
+type: docker
+name: default
+
+steps:
+- name: cargo_check
+  image: rust
+  commands:
+  - rustup component add clippy
+  - cargo clippy -- -D warnings
+  - cargo test --all-features
+
+