* feat(headers): add functions to remove and get extra headers (#572)
  * client.setExtraHeader('X-cool-header','hello there');
  * client.getExtraHeader('X-cool-header'); //hello there
  * client.unsetExtraHeader('X-cool-header');
  * client.getExtraHeader('X-cool-header'); //undefined
* feat(deprecation): use console.warn to be more visible
* refact(rules): Adapt to latest JSON schema for Query Rules