[Tests] clean up travis.yml a bit

Author: ljharb

.travis.yml

@@ -1,7 +1,8 @@
 language: node_js
-os:
- - linux
 node_js:
+  - "13"
+  - "12"
+  - "11"
   - "10"
   - "9"
   - "8"
@@ -13,15 +14,11 @@ node_js:
   - "iojs-v2"
   - "iojs-v1"
   - "0.12"
-before_install:
-  - 'nvm install-latest-npm'
-install:
-  - 'if [ "${TRAVIS_NODE_VERSION}" = "0.6" ] || [ "${TRAVIS_NODE_VERSION}" = "0.9" ]; then nvm install --latest-npm 0.8 && npm install && nvm use "${TRAVIS_NODE_VERSION}"; else npm install; fi;'
-script:
-  - 'if [ -n "${PRETEST-}" ]; then npm run pretest ; fi'
-  - 'if [ -n "${POSTTEST-}" ]; then npm run posttest ; fi'
-  - 'if [ -n "${COVERAGE-}" ]; then npm run coverage ; fi'
-  - 'if [ -n "${TEST-}" ]; then npm run tests-only ; fi'
+import:
+  - ljharb/travis-ci:node/latest-npm.yml
+  - ljharb/travis-ci:node/greenkeeper.yml
+  - ljharb/travis-ci:node/dependabot.yml
+script: 'npm run tests-only'
 sudo: false
 env:
   - TEST=true
@@ -30,13 +27,12 @@ matrix:
   include:
     - node_js: "lts/*"
       env: PRETEST=true
+      script: 'npm run pretest'
   allow_failures:
     - node_js: "9"
     - node_js: "7"
     - node_js: "5"
     - node_js: "iojs-v3"
     - node_js: "iojs-v2"
     - node_js: "iojs-v1"
-    - os: osx
     - env: TEST=true ALLOW_FAILURE=true
-    - env: COVERAGE=true