Update drone.yml to new format

.drone.yml

@@ -1,18 +1,15 @@
-workspace:
+kind: pipeline
-  base: /go
+name: default
-  path: src/deadbeef.codes/steven/mandelmapper
 
-pipeline:
+steps:
-  build:
+- name: build
-    image: golang:latest
+  image: golang
-    commands:
+  pull: always
-      - go version
+  environment:
-      - go get
+    GOOS: linux
-      - CGO_ENABLED=0 GOOS=linux go build -ldflags '-w'
+    GOARCH: amd64
-  publish:
+    CGO_ENABLED: 0
-    image: plugins/docker
+  commands:
-    repo: deadbeef.codes:5000/mandelmapper
+    - go version
-    registry: deadbeef.codes:5000
+    - go get
-    tags:
+    - go build -ldflags '-w'
-      - latest
-      - ${DRONE_COMMIT}