Bug fix of Pull Request #39

I fix bugs of #39 by two changes.

* use `detect_platform` method instead of `Motion::Project::App.template`
  * When IB::Project#write is executed via rake command, IB::Project#write can reference to Motion::Project::App.template, but in spec test, it can't that. 
  * Almost same result those two solution.
* incidentally update `xcodeproj` gem (patch update)
  * see https://github.com/CocoaPods/Xcodeproj/commit/bd32de6bbc7d9d95a09c517f1ea0ae4f894eb335