Added share names for older iOS versions.

Author: Edward Smith

Branch-SDK/Branch-SDK/BranchActivityItemProvider.m

@@ -94,6 +94,12 @@ + (NSString *)humanReadableChannelWithActivityType:(NSString *)activityString {
         @"WeChat", @"com.tencent.xin.sharetimeline",
         @"LINE", @"jp.naver.line.Share",
 		@"Pinterest", @"pinterest.ShareExtension",
+
+        //  Keys for older app versions --
+
+        @"Facebook",    @"com.facebook.Facebook.ShareExtension",
+        @"Twitter",     @"com.atebits.Tweetie2.ShareExtension",
+
         nil
     ];
     // Set to a more human readible sting if we can identify it