Replace Gitlab CI with Drone

.drone.yml

@@ -0,0 +1,22 @@
+kind: pipeline
+type: docker
+name: rust-stable
+
+steps:
+  - name: stable
+    image: rust:latest
+    commands:
+      - cargo build --verbose
+      - cargo test
+
+---
+kind: pipeline
+type: docker
+name: rust-nightly
+
+steps:
+  - name: nightly
+    image: rustlang/rust:nightly
+    commands:
+      - cargo build --verbose
+      - cargo test

.gitlab-ci.yml

@@ -1,14 +0,0 @@
-stages:
-  - build
-
-rust-latest:
-  stage: build
-  image: rust:latest
-  script:
-    - cargo build --verbose
-
-rust-nightly:
-  stage: build
-  image: rustlang/rust:nightly
-  script:
-    - cargo build --verbose