tools: add objectLiteralShorthandProperties to .eslintrc

Required to make linting pass for using object literal
shorthand properties.

PR-URL: https://github.com/nodejs/io.js/pull/1760
Reviewed-By: Chris Dickinson <christopher.s.dickinson@gmail.com>

.eslintrc

@@ -9,6 +9,7 @@ ecmaFeatures:
   binaryLiterals: true
   generators: true
   forOf: true
+  objectLiteralShorthandProperties: true
 
 rules:
   # Possible Errors