Update TravisCI configuration

Author: Nir Maoz

.travis.yml

@@ -3,17 +3,10 @@ language: node_js
 node_js:
   - "node"
   - "lts/*"
-  - "6"
-install:
-  - npm install react@^16.0.0 --no-save
-  - npm install
+before_script:
   - npm run compile
   - npm run dist
 env:
   - TEST_SUBJECT=src
   - TEST_SUBJECT=lib
   - TEST_SUBJECT=dist
-matrix:
-  exclude:
-    - node_js: "6"
-      env: TEST_SUBJECT=src