title: How to replace english abbreviated form to their dictionary form
body: <p>I'm working on a system to analyze texts in english: I use stanford-core nlp to make sentences from whole documents and to make tokens from sentences. I also use the maxent tagger to get tokens pos tags. 
  Now, considering that I use this corpus to build a supervised classifier, it would be good if I could replace any word like 're, 's, havin, sayin', etc. to its standard form(are, is, having, saying). I've been searching for some english dictionary file, but I don't know how to use it. There are so many distinct cases to consider that I don't think it's an easy task to realize: is there some similar work or whole project that I could use? </p>