title: Convert threeten LocalDate to YearMonth
body: <p>I have a <code>LocalDate</code> which I need to convert to <code>YearMonth</code>. 
  I am using ThreeTen API (Backport of JSR-310 to Java SE 7). 
  Is there anyway I can do this?</p>
  
  <p>I tried this in Joda-Time but in ThreeTen it is not offered. </p>
  
  <pre><code>LocalDate date;
  new YearMonth(date.getYear(), date.getMonthOfYear());
  </code></pre>