chore(travis): update node version

Vasil Chimev · web-flow · commit b48ad91797d0 · 2017-07-18T16:54:56.000+03:00
node@6.9.1 installs npm@3.10.8 by default and CLI@next fails to install on it. Issue: NativeScript/nativescript-cli#2980
diff --git a/.travis.yml b/.travis.yml
@@ -1,6 +1,6 @@
 env:
   global:
-  - NODE_VERSION=6.9.1
+  - NODE_VERSION=6.11.1
   - EMULATOR_API_LEVEL=19
   - ANDROID_VERSION=23
   - ANDROID_BUILD_TOOLS_VERSION=23.0.1
