[Tests] up to node v8.6; use nvm install-latest-npm to ensure new npm doesn’t break old node

Author: ljharb

.travis.yml

@@ -2,7 +2,7 @@ language: node_js
 os:
  - linux
 node_js:
-  - "8.2"
+  - "8.6"
   - "7.10"
   - "6.11"
   - "5.12"
@@ -14,10 +14,9 @@ node_js:
   - "0.10"
   - "0.8"
 before_install:
-  - 'if [ "${TRAVIS_NODE_VERSION}" = "0.6" ]; then npm install -g [email protected] ; elif [ "${TRAVIS_NODE_VERSION}" != "0.9" ]; then case "$(npm --version)" in 1.*) npm install -g [email protected] ;; 2.*) npm install -g npm@2 ;; esac ; fi'
-  - 'if [ "${TRAVIS_NODE_VERSION}" != "0.6" ] && [ "${TRAVIS_NODE_VERSION}" != "0.9" ]; then if [ "${TRAVIS_NODE_VERSION%${TRAVIS_NODE_VERSION#[0-9]}}" = "0" ] || [ "${TRAVIS_NODE_VERSION:0:4}" = "iojs" ]; then npm install -g [email protected] ; else npm install -g npm; fi; fi'
+  - 'nvm install-latest-npm'
 install:
-  - 'if [ "${TRAVIS_NODE_VERSION}" = "0.6" ]; then nvm install 0.8 && npm install -g [email protected] && npm install -g [email protected] && npm install -g npm@2 && npm install && nvm use "${TRAVIS_NODE_VERSION}"; else npm install; fi;'
+  - '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'
@@ -29,6 +28,14 @@ env:
 matrix:
   fast_finish: true
   include:
+    - node_js: "8.5"
+      env: TEST=true ALLOW_FAILURE=true
+    - node_js: "8.4"
+      env: TEST=true ALLOW_FAILURE=true
+    - node_js: "8.3"
+      env: TEST=true ALLOW_FAILURE=true
+    - node_js: "8.2"
+      env: TEST=true ALLOW_FAILURE=true
     - node_js: "8.1"
       env: TEST=true ALLOW_FAILURE=true
     - node_js: "8.0"