Improve css-sel2 detection perf (#88)

Author: alanhussey

data/features.js

@@ -4,11 +4,16 @@ var pats = {
   brackets: /(\[[^\]]*\]|\([^\)]*\))/.source,
   nobrackets: /[^\[\]\(\)]/.source
 }
-function matchOutsideOfBrackets (pat) {
-  if (pat instanceof RegExp) {
-    pat = pat.source
+function matchOutsideOfBrackets(pat) {
+  if (!(pat instanceof RegExp)) {
+    throw new TypeError('matchOutsideOfBrackets expects a RegExp')
+  }
+  var fullPat = new RegExp(
+    '^(' + pats.brackets + '?' + pats.nobrackets + '*)*' + pat.source
+  )
+  return function match(str) {
+    return pat.test(str) && fullPat.test(str)
   }
-  return new RegExp('^(' + pats.brackets + '?' + pats.nobrackets + '*)*' + pat)
 }
 
 module.exports = {