Exclude deployment for pull requests, move docker and sudo requirements to deploy step

.travis.yml

@@ -1,16 +1,11 @@
-sudo: required
-
 language: go
 go:
-  - 1.13
-
-services:
-  - docker
+  - "1.13"
 
 stages:
   - test
   - name: deploy
-    if: branch = master OR tag IS present
+    if: env(TRAVIS_PULL_REQUEST) = false AND (branch = master OR tag IS present)
 
 install:
   - go get -u github.com/golang/dep/cmd/dep
@@ -22,7 +17,11 @@ jobs:
       script:
         - go test -v -race -coverprofile=coverage.txt -covermode=atomic ./...
         - bash <(curl -s https://codecov.io/bash)
+
     - stage: deploy
+      sudo: required
+      services:
+        - docker
       script:
         - docker login -u="$DOCKER_USERNAME" -p="$DOCKER_PASSWORD"
         - export DOCKER_TAG="${TRAVIS_TAG:-dev}"