moving to use indexof

Author: aliabbasrizvi

packages/optimizely-sdk/lib/core/project_config/index.js

@@ -140,7 +140,7 @@ module.exports = {
  var attribute = projectConfig.attributeKeyMap[attributeKey];
  if (attribute) {
  return attribute.id;
- } else if (attributeKey.startsWith(RESERVED_ATTRIBUTE_PREFIX)) {
+ } else if (attributeKey.indexOf(RESERVED_ATTRIBUTE_PREFIX) === 0) {
  return attributeKey;
  }