Tweak travis node versions

Author: brianc

.travis.yml

@@ -8,47 +8,29 @@ env:
 
 matrix:
   include:
-    - node_js: "4"
+    - node_js: "lts/argon"
       addons:
         postgresql: "9.6"
-    - node_js: "5"
-      addons:
-        postgresql: "9.6"
-    - node_js: "6"
+    - node_js: "lts/boron"
       addons:
         postgresql: "9.1"
       dist: precise
-    - node_js: "6"
+    - node_js: "lts/boron"
       addons:
         postgresql: "9.2"
-    - node_js: "6"
+    - node_js: "lts/boron"
       addons:
         postgresql: "9.3"
-    - node_js: "6"
+    - node_js: "lts/boron"
       addons:
         postgresql: "9.4"
-    - node_js: "6"
+    - node_js: "lts/boron"
       addons:
         postgresql: "9.5"
-    - node_js: "6"
+    - node_js: "lts/boron"
       addons:
         postgresql: "9.6"
-    - node_js: "8"
-      addons:
-        postgresql: "9.1"
       dist: precise
-    - node_js: "8"
-      addons:
-        postgresql: "9.2"
-    - node_js: "8"
-      addons:
-        postgresql: "9.3"
-    - node_js: "8"
-      addons:
-        postgresql: "9.4"
-    - node_js: "8"
-      addons:
-        postgresql: "9.5"
     - node_js: "8"
       addons:
         postgresql: "9.6"