tools: enable space-in-parens ESLint rule

Ref: http://eslint.org/docs/rules/space-in-parens.html
PR-URL: #4753
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>

Author: silverwind

.eslintrc

@@ -65,8 +65,10 @@ rules:
   eol-last: 2
   ## no trailing spaces
   no-trailing-spaces: 2
-  # require space after keywords, eg 'for (..)'
+  ## require space after keywords, eg 'for (..)'
   space-after-keywords: 2
+  ## no leading/trailing spaces in parens
+  space-in-parens: [2, "never"]
 
   # ECMAScript 6
   # list: http://eslint.org/docs/rules/#ecmascript-6