title: Determine user's "Temperature Unit" setting on iOS 10 (Celsius / Fahrenheit)
body: <p>iOS 10 adds the ability for the user to set their "Temperature Unit" choice under Settings > General > Language &amp; Region > Temperature Unit.</p>
  
  <p>How can my app programmatically determine this setting so it can display the right temperature unit? I poured through NSLocale.h and didn't see anything relevant.</p>
  
  <p>(Before iOS 10, it was sufficient to test if the locale used metric and assume that metric users want to use Celsius. This is no longer the case.)</p>