add drone configuration

.drone.yml

@@ -0,0 +1,16 @@
+kind: pipeline
+type: docker
+name: mailApp
+
+trigger:
+  branch:
+    - master
+  event:
+    - push
+
+steps:
+  - name: testBuild
+    image: rust:1.56
+    commands:
+      - cargo build --verbose --all
+      - cargo test --verbose --all