ci: use shared Travis config from semantic-release master branch

Author: pvdlg

.travis.yml

@@ -2,7 +2,7 @@ version: ~> 1.0
 
 import:
   - semantic-release/semantic-release:.travis/node.yml
-  - semantic-release/semantic-release:.travis/node-versions.yml@beta
+  - semantic-release/semantic-release:.travis/node-versions.yml
   - semantic-release/semantic-release:.travis/semantic-release.yml
   - semantic-release/semantic-release:.travis/greenkeeper.yml
   - semantic-release/semantic-release:.travis/codecov.yml