title: Tokenizer that splits up words with underscores in them but also retains a full version
body: <p>I'm implementing an Elasticsearch search for content that has filesnames in it, such as 
  "golf_master_2009.xls". I'd like a tokenizer that splits this up into at least the following tokens: "golf", "master", "golf_master_2009.xml". Now I have to use wildcards (for example "<em>master</em>") if I want to search for it without specifying the full filename.</p>