fix(ci): refactor travis config

Add some Node configurations (10 & 12 on both mac & linux)
Use a workaround to have a working coverage command
yarnpkg/yarn#6746

.travis.yml

@@ -1,17 +1,35 @@
 language: node_js
-node_js:
-  - "11"
 
 install:
   - yarn
 
 matrix:
   include:
     - script:
-        - yarn build:all
-        - yarn coverage
-        - yarn run codecov
+      - yarn build:all
+      - npm run coverage
+      - npm run codecov
       name: "Coverage"
+      node_js: 12
+    - script:
+      - yarn build:all
+      - yarn test
+      name: "Node 10"
+      node_js: 10
+    - script:
+      - yarn test
+      name: "Node 12"
+      node_js: 12
+    - script:
+      - yarn test
+      name: "Node 10 on mac"
+      os: osx
+      node_js: 10
+    - script:
+      - yarn test
+      name: "Node 12 on mac"
+      os: osx
+      node_js: 12
     - script: yarn karma --browsers ChromeWindows10
       name: "Latest Chrome on Windows 10"
     - script: yarn karma --browsers Chrome70Windows7
@@ -32,6 +50,5 @@ matrix:
       name: "Chrome Android 5"
     - script: yarn karma --browsers iOS12
       name: "Safari iOS 12"
-  allow_failures:
     - script: yarn karma --browsers Safari12Mojave
       name: "Safari 12 on OS X Mojave"