title: Error when running on iOS 6 but not iOS 7
body: <p>I am trying to run my project on iOS 6 and I have set all the appropriate build settings to let me do so, but when I run on iOS 6 I get this error:</p>
  
  <pre><code>dyld: Symbol not found: _OBJC_CLASS_$_NSURLSession
    Referenced from: /var/mobile/Applications/8AC09960-A403-413E-B70A-E03DB2AF5844/Flywheel.app/Flywheel
    Expected in: /System/Library/Frameworks/Foundation.framework/Foundation
   in /var/mobile/Applications/8AC09960-A403-413E-B70A-E03DB2AF5844/Flywheel.app/Flywheel
  </code></pre>
  
  <p>What gives??  iOS 7 works fine.</p>