Remove unnecessary field.
Fix the bug introduce by @justinmuller in e7061f0012ce118df6ab269ee6468c9f2c9daddb: The captured API Key was not being passed back to MainScreen.

Previously MainScreen was being killed when BarCodeReaderActivity was started, BarCodeReaderActivity would then restart MainScreen with an Intent that contained the API Key.  Now, MainScreen is no longer killed, and BarCodeReaderActivity passes the API Key back via MainScreen#onActivityResult(int, int, Intent data)
Merge pull request #24 from Letme/bug-fix

Fix bug introduced in PR # 23