Make possible to run Example app in Xcode6

Rerun `pod install` with the latest CocoaPods
Put CocoaPods into Gemfile
Remove all pods added for testing because they were not actually used.
Upgrade test target to use XCTest instead of SenTesting
Refactor: `isOS7` -> `isOS7OrHigher`
Use `preferredContentSize` on iOS7 and above
Alert user if no Camera access on iOS8
Merge #15