AppBuilder compatibility

Hi, the current version of Estimote SDK for iOS was compiled with XCode 6 and links to `Metal` which requires iOS 8 SDK. This is fine for local build of course but AppBuilder is not using iOS 8 SDK yet so I obviously couldn't get it to compile nicely in the cloud.

Estimote SDK 2.1.0 was the last one built with XCode 5 and seems to work fine (after changing a bit of code in our `.m` file).

I understand if you don't want this in your repo but as I only commented some stuff out we should be able to easily add it back in when AppBuilder compiles agains iOS 8 SDK.