title: Time limit for mixed integer programming with Python PuLP
body: <p>I've been using <a href="http://pythonhosted.org/PuLP/" rel="noreferrer">PuLP</a> to solve a particular mixed integer linear program (MIP) I am interested in. However, as the problem size grows, PuLP is taking too long. I want to be able to run the solver for some time and terminate it prematurely if its taking to long and obtain the best feasible solution so-far computed. I have tried manually timing the solver out with signal, but the variables are all "None".</p>
  
  <p>I've looked at the documentation and PuLP does not seem to support this, though as I understand it, most of the solver routines it calls do. Is there a way to impose a time limit for PuLP?</p>