title: Get the weeks starting and ending date from year and calendar week with javascript
body: <p>I need to get the weeks starting and ending date with Javascript/ moment.js</p>
  
  <p>As input i have two values: year and week, which is the isoweek of moment.js</p>
  
  <p>year = '2016'
  week = '1'</p>
  
  <p>should give me the 04.01.2016 and 10.01.2016 </p>
  
  <p>where the date has the german format moment().format('DD.MM.YYYY');</p>