Update fibers dependency (#174)

* Update fibers dependency

* Drop Travis Node.js support for v0.12 & v5. Add travis support for v8, v9, v10.

Author: renarsvilnis

.travis.yml

@@ -6,10 +6,11 @@ env:
 sudo: false
 language: node_js
 node_js:
-- "0.12"
 - "4"
-- "5"
 - "6"
+- "8"
+- "9"
+- "10"
 script: npm test
 after_script: npm run coveralls
 addons: