Issue title: Update Firebase framework for 64-bit slice
 Issue body: FYI, you'll need to remove the 64-bit option (`arm64`) from the `Active Architectures` from the project settings to get the project to compile since the Firebase framework wasn't build with a 64-bit slice. Also, you'll need to set `Build Active Architecture Only` to `NO`

> ld: warning: ignoring file /Users/rob/Downloads/firechat-ios-master/Firebase.framework/Firebase, missing required architecture x86_64 in file /Users/rob/Downloads/firechat-ios-master/Firebase.framework/Firebase (3 slices)

 Comments: 
 Comment 0: Thanks for the heads up. I believe e009200ee6517a6c8c2a1eec94ddc173fbfa46b7 should fix this by upgrading Firebase to version 1.1.12.

{'source': 'GithubIssues', 'repo_name_with_owner': 'FirebaseExtended/firechat-ios', 'issue_id': 41403946, 'repo_stars': 246.0}