title: Linker errors with ParseUI iOS and CocoaPods
body: <p>I was attempting to build an app using Parse and wanted to give ParseUI a shot.  I imported Parse's main SDK using Cocoa pods, and it worked fine.  When I decided to add ParseUI, I ran into problems.  </p>
  
  <pre><code>Undefined symbols for architecture i386:
    "_OBJC_CLASS_$_BFTaskCompletionSource", referenced from:
        objc-class-ref in PFImageView.o
    "_OBJC_CLASS_$_PFProduct", referenced from:
        objc-class-ref in PFProductTableViewController.o
       (maybe you meant: _OBJC_CLASS_$_PFProductTableViewController)
    "_OBJC_CLASS_$_PFPurchase", referenced from:
        objc-class-ref in PFProductTableViewController.o
       (maybe you meant: _OBJC_CLASS_$_PFPurchaseTableViewCell)
    "_OBJC_CLASS_$_PFQuery", referenced from:
        objc-class-ref in PFQueryTableViewController.o
       (maybe you meant: _OBJC_CLASS_$_PFQueryTableViewController)
    "_OBJC_CLASS_$_PFTwitterUtils", referenced from:
        objc-class-ref in PFLogInViewController.o
    "_OBJC_CLASS_$_PFUser", referenced from:
        objc-class-ref in PFLogInViewController.o
        objc-class-ref in PFSignUpViewController.o
    "_PFParseErrorDomain", referenced from:
        -[PFImageView loadInBackground:] in PFImageView.o
        ___32-[PFImageView loadInBackground:]_block_invoke30 in PFImageView.o
        -[PFSignUpViewController _signUpAction] in PFSignUpViewController.o
        -[PFSignUpViewController _signUpDidFailWithError:] in PFSignUpViewController.o
        -[PFImageView loadInBackground:] in PFImageView.o
        ___32-[PFImageView loadInBackground:]_block_invoke30 in PFImageView.o
        -[PFSignUpViewController _signUpAction] in PFSignUpViewController.o
        -[PFSignUpViewController _signUpDidFailWithError:] in PFSignUpViewController.o
    "_kPFErrorCacheMiss", referenced from:
        ___48-[PFQueryTableViewController loadObjects:clear:]_block_invoke in PFQueryTableViewController.o
    "_kPFErrorInvalidEmailAddress", referenced from:
        -[PFSignUpViewController _signUpDidFailWithError:] in PFSignUpViewController.o
    "_kPFErrorInvalidImageData", referenced from:
        ___32-[PFImageView loadInBackground:]_block_invoke30 in PFImageView.o
    "_kPFErrorUnsavedFile", referenced from:
        -[PFImageView loadInBackground:] in PFImageView.o
    "_kPFErrorUserEmailMissing", referenced from:
        -[PFSignUpViewController _signUpDidFailWithError:] in PFSignUpViewController.o
    "_kPFErrorUserEmailTaken", referenced from:
        -[PFSignUpViewController _signUpDidFailWithError:] in PFSignUpViewController.o
    "_kPFErrorUserPasswordMissing", referenced from:
        -[PFSignUpViewController _signUpDidFailWithError:] in PFSignUpViewController.o
    "_kPFErrorUsernameMissing", referenced from:
        -[PFSignUpViewController _signUpDidFailWithError:] in PFSignUpViewController.o
    "_kPFErrorUsernameTaken", referenced from:
        -[PFSignUpViewController _signUpDidFailWithError:] in PFSignUpViewController.o
  ld: symbol(s) not found for architecture i386
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  </code></pre>
  
  <p>I've attempted things like forcing the inclusion of the Parse.framework for the linking of ParseUI, but it didnt seem to help.  I'm not an expert with cocoapods or with XCode, so I don't know if there's something obvious I'm missing.</p>
  
  <p>I've tried cocoapods 0.35 and 0.36-beta-1.   This is a swift project, so I don't know if that could be causing some of the problems.</p>