remove build with node 4; remove slack unused slack config

Author: trestoa

.travis.yml

@@ -3,7 +3,6 @@ node_js:
 - 8
 - 7
 - 6
-- 4
 env:
   - CC=clang CXX=clang++
 addons:
@@ -27,9 +26,3 @@ script:
 - grunt swagger-validate
 - grunt build
 - npm test
-notifications:
-  slack:
-    rooms:
-      secure: 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
-    on_success: change
-    on_failure: always