Reduce node versions on Travis

Keep only latest, 10 (current LTS), and 7.6 (minimum required).

Author: daquinoaldo

.travis.yml

@@ -5,30 +5,6 @@ os:
 language: node_js
 node_js:
 - node
-- 11
 - 10
-- 10.15.1
-- 10.15.0
-- 10.14.2
-- 10.14.1
-- 10.14.0
-- 10.13
-- 9
-- 8
-- 8.15
-- 8.14.1
-- 8.14.0
-- 8.13
-- 8.12
-- 8.11.4
-- 8.11.3
-- 8.11.2
-- 8.11.1
-- 8.11.0
-- 8.10
-- 8.9.4
-- 8.9.3
-- 8.9.2
-- 8.9.1
-- 8.9.0
+- 7.6
 after_success: npm run coveralls