[Tests] skip node 6 and 8 tests in all but the latest React

 - node 4 and 10 are still tested for everything
 - if any regressions occur, those will be unexcluded

Author: ljharb

.travis.yml

@@ -45,6 +45,43 @@ matrix:
       env: KARMA=true REACT=15
     - node_js: "6"
       env: KARMA=true REACT=16
+  exclude:
+    - node_js: "6"
+      env: REACT=0.13
+    - node_js: "8"
+      env: REACT=0.13
+    - node_js: "6"
+      env: REACT=0.14
+    - node_js: "8"
+      env: REACT=0.14
+    - node_js: "6"
+      env: REACT=15.4
+    - node_js: "8"
+      env: REACT=15.4
+    - node_js: "6"
+      env: REACT=15.5
+    - node_js: "8"
+      env: REACT=15.5
+    - node_js: "6"
+      env: REACT=16.0
+    - node_js: "8"
+      env: REACT=16.0
+    - node_js: "6"
+      env: REACT=16.1
+    - node_js: "8"
+      env: REACT=16.1
+    - node_js: "6"
+      env: REACT=16.2
+    - node_js: "8"
+      env: REACT=16.2
+    - node_js: "6"
+      env: REACT=16.3
+    - node_js: "8"
+      env: REACT=16.3
+    - node_js: "6"
+      env: REACT=16.4
+    - node_js: "8"
+      env: REACT=16.4
 env:
   - REACT=16.5
   - REACT=16.4