Set Node.js version to 10 in order to fix TravisCI build (#520)

Most of the other ones are erroing on TravisCI, so trying to set a
reasonable version for the time being.

* Address a few issues with TravisCI config

- fail_fast is actually fast_finish
- operating system was not explicitely set
- sudo is no longer necessary

.travis.yml

@@ -1,12 +1,11 @@
----
 language: node_js
 node_js:
-  - "8"
+  - 10
 
 addons:
   chrome: stable
 
-sudo: false
+os: linux
 dist: trusty
 
 cache:
@@ -22,7 +21,7 @@ branches:
     - master
 
 jobs:
-  fail_fast: true
+  fast_finish: true
   allow_failures:
     - env: EMBER_TRY_SCENARIO=ember-canary