title: Issue in full calendar first day option
body: <p>I have configured my week start on Wednesday. I am setting cal date as jan 7(tuesday). now i am going to week view. Its shows the week date from 2nd jan to 8th jan. What I except is, for given date 7, its should choose week duration from jan 5(sunday) to jan 11. Please refer the screen shot and help me. </p>
  
  <p><a href="http://s30.postimg.org/epq10h2o1/edited.png" rel="noreferrer">http://s30.postimg.org/epq10h2o1/edited.png</a></p>