title: How to get number of followers using Tweepy in a specific date?
body: <p>I would like to know if exists any way to get the number of followers of an account using Tweepy (or with raw Twitter API) in a specific date. 
  I've been watching out to several ways to do this without success. Now I'm saving this number every day to can build a special graphics but I would like to do this with old accounts to know their growth.</p>
  
  <p>I've seen this kind of histograms in some apps and tools, because of this I think that this is possible but I don´t find how.</p>
  
  <p>Any idea? Thanks! </p>