Workaround for old SpiderMonkey builds

Fixes #189

mustache.js

@@ -38,8 +38,14 @@ var Mustache = (typeof module !== "undefined" && module.exports) || {};
   var curlyRe = /\s*\}/;
   var tagRe = /#|\^|\/|>|\{|&|=|!/;
 
+  // Workaround for https://issues.apache.org/jira/browse/COUCHDB-577
+  // See https://github.com/janl/mustache.js/issues/189
+  function testRe(re, string) {
+    return RegExp.prototype.test.call(re, string);
+  }
+
   function isWhitespace(string) {
-    return !nonSpaceRe.test(string);
+    return !testRe(nonSpaceRe, string);
   }
 
   var isArray = Array.isArray || function (obj) {