title: iOS app crashes when Podfile has 'use_frameworks!' option
body: <p>I have a Single View app setup with CocoaPods that includes only two pods, 'MBProgressHUB' and 'ImojiSDK'.</p>
  
  <p>When CocoaPods is setup as a static library, the project builds and runs normally. When I configure CocoaPods to use frameworks, by including the 'use_frameworks!' flag in the Podfile, the project builds, but crashes when run. </p>
  
  <p>Question is, why does it run fine as a static library, but not when using frameworks?</p>
  
  <p>The crash happens when I try to create a new ImojiSDK session in the view's viewDidLoad:</p>
  
  <pre><code>IMImojiSession *session = [IMImojiSession imojiSession]; //THIS IS WHERE IT CRASHES
  session.contentCache = [[NSCache alloc] init];
  session.contentCache.countLimit = 100;
  </code></pre>
  
  <p>Below are the Podfile and crash output from Xcode:</p>
  
  <h1>PODFILE:</h1>
  
  <pre><code># Uncomment this line to define a global platform for your project
  # platform :ios, '6.0'
  
  use_frameworks!
  
  pod 'MBProgressHUD'
  pod 'ImojiSDK'
  </code></pre>
  
  <h1>CRASH OUTPUT:</h1>
  
  <pre><code>2015-07-20 14:05:18.031 imoji[19887:323843] +[BFTask im_concurrentBackgroundTaskWithBlock:]: unrecognized selector sent to class 0x1041b6878
  2015-07-20 14:05:18.035 imoji[19887:323843] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '+[BFTask im_concurrentBackgroundTaskWithBlock:]: unrecognized selector sent to class 0x1041b6878'
  *** First throw call stack:
  (
      0   CoreFoundation                      0x0000000104aafc65 __exceptionPreprocess + 165
      1   libobjc.A.dylib                     0x0000000104746bb7 objc_exception_throw + 45
      2   CoreFoundation                      0x0000000104ab6fad +[NSObject(NSObject) doesNotRecognizeSelector:] + 205
      3   CoreFoundation                      0x0000000104a0d13c ___forwarding___ + 988
      4   CoreFoundation                      0x0000000104a0ccd8 _CF_forwarding_prep_0 + 120
      5   imoji                               0x0000000104003962 -[IMMutableImojiSessionStoragePolicy performCleanupOnOldImages] + 93
      6   imoji                               0x0000000104002c4f -[IMMutableImojiSessionStoragePolicy initWithCachePath:persistentPath:] + 175
      7   imoji                               0x000000010400ec6d +[IMImojiSessionStoragePolicy temporaryDiskStoragePolicy] + 210
      8   imoji                               0x0000000104003dfc -[IMImojiSession init] + 76
      9   imoji                               0x000000010400e8c7 +[IMImojiSession imojiSession] + 41
      10  imoji                               0x0000000103fd6b8c -[ViewController viewDidLoad] + 76
      11  UIKit                               0x000000010526d1d0 -[UIViewController loadViewIfRequired] + 738
      12  UIKit                               0x000000010526d3ce -[UIViewController view] + 27
      13  UIKit                               0x0000000105188289 -[UIWindow addRootViewControllerViewIfPossible] + 58
      14  UIKit                               0x000000010518864f -[UIWindow _setHidden:forced:] + 247
      15  UIKit                               0x0000000105194de1 -[UIWindow makeKeyAndVisible] + 42
      16  UIKit                               0x0000000105138417 -[UIApplication _callInitializationDelegatesForMainScene:transitionContext:] + 2732
      17  UIKit                               0x000000010513b19e -[UIApplication _runWithMainScene:transitionContext:completion:] + 1349
      18  UIKit                               0x000000010513a095 -[UIApplication workspaceDidEndTransaction:] + 179
      19  FrontBoardServices                  0x00000001085585e5 __31-[FBSSerialQueue performAsync:]_block_invoke_2 + 21
      20  CoreFoundation                      0x00000001049e341c __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
      21  CoreFoundation                      0x00000001049d9165 __CFRunLoopDoBlocks + 341
      22  CoreFoundation                      0x00000001049d8f25 __CFRunLoopRun + 2389
      23  CoreFoundation                      0x00000001049d8366 CFRunLoopRunSpecific + 470
      24  UIKit                               0x0000000105139b02 -[UIApplication _run] + 413
      25  UIKit                               0x000000010513c8c0 UIApplicationMain + 1282
      26  imoji                               0x0000000103fd6fef main + 111
      27  libdyld.dylib                       0x0000000106579145 start + 1
  )
  libc++abi.dylib: terminating with uncaught exception of type NSException
  (lldb) 
  </code></pre>