Add code to allow API key to be set outside of info plist.

@sonicbee9 - what do you think about allowing the consumer the ability to set the API key outside of the app's info plist?  It's very easy to crack open any app on the App Store and view its info plist.  It's a security risk to place an API key in the info plist.

This PR shows an example of placing the API key in code rather than in the info plist. (The info plist approach still works fine the way it is implemented.)  There are still ways to get to the API key even if it is compiled into a binary, but it's many orders of magnitude more difficult than cracking open an app bundle and taking a peek at the plist.