Make is64 property part of the updater

lib/SlackBuilder/Package.hs

@@ -34,7 +34,6 @@ data Package = Package
 data Download = Download
     { download :: URI
     , md5sum :: Digest MD5
-    , is64 :: Bool
     } deriving (Eq, Show)
 
 -- | Package maintainer information.
@@ -74,5 +73,6 @@ renderDownloadWithVersion (DownloadTemplate components) version =
 -- | Function used to get the latest version of a source.
 data Updater = Updater
     { detectLatest :: SlackBuilderT (Maybe Text)
+    , is64 :: Bool
     , getVersion :: Text -> Text -> SlackBuilderT Download
     }