TLMetaResolver 是一个 UIWebView 的扩展，可以添加在已加载网页上解析 meta 标签的能力。
使用：
func resolveMetaTags (onComplete: TLMetaResolverComplete) func resolveMetaTags (fetchUrl: TLMetaResolverFetchURL?, _ fetchImage: TLMetaResolverFetchURL?, _ onComplete: TLMetaResolverComplete)
