Add Drone CI integration

Author: lafriks

.drone.yml

@@ -0,0 +1,21 @@
+kind: pipeline
+name: testing
+
+clone:
+  depth: 50
+
+steps:
+  - name: lint
+    image: golang:1.11
+    pull: true
+    commands:
+      - go tool vet -all -shadowstrict .
+      - get -u github.com/mgechev/revive
+      - revive -config .revive.toml -exclude=./vendor/... ./...
+
+  - name: test
+    image: golang:1.11
+    pull: true
+    commands:
+      - go test -v .
+      - go vet

.revive.toml

@@ -0,0 +1,25 @@
+ignoreGeneratedHeader = false
+severity = "warning"
+confidence = 0.8
+errorCode = 1
+warningCode = 1
+
+[rule.blank-imports]
+[rule.context-as-argument]
+[rule.context-keys-type]
+[rule.dot-imports]
+[rule.error-return]
+[rule.error-strings]
+[rule.error-naming]
+[rule.exported]
+[rule.if-return]
+[rule.increment-decrement]
+[rule.var-naming]
+[rule.var-declaration]
+[rule.package-comments]
+[rule.range]
+[rule.receiver-naming]
+[rule.time-naming]
+[rule.unexported-return]
+[rule.indent-error-flow]
+[rule.errorf]