title: docopt boolean arg python
body: <p>I use following args for my script with doctopt</p>
  
  <pre><code>Usage:
  GaussianMixture.py --snpList=File --callingRAC=File
  
  Options:
  -h --help     Show help.
  snpList     list snp txt
  callingRAC      results snp
  </code></pre>
  
  <p>I would like to add an argument that have a conditional consequence on my script : correct my datas or don't correct my datas. Something like :</p>
  
  <pre><code>Usage:
  GaussianMixture.py --snpList=File --callingRAC=File  correction(--0 | --1)
  
  Options:
  -h --help     Show help.
  snpList     list snp txt
  callingRAC      results snp
  correction      0 : without correction | 1 : with correction 
  </code></pre>
  
  <p>And I would like to add in my script an <code>if</code> in some functions </p>
  
  <pre><code>def func1():
    if args[correction] == 0:
        datas = non_corrected_datas
    if args[correction] == 1:
        datas = corrected_datas
  </code></pre>
  
  <p>But I don't know how to write it in the usage neither in my script.</p>