Expand Xcode README.

Closes #222

developer-xcode/README Xcode Project.md

diff --git a/developer-xcode/README Xcode Project.md b/developer-xcode/README Xcode Project.md
index f3c2521..8ae1f65 100644
--- a/developer-xcode/README Xcode Project.md
+++ b/developer-xcode/README Xcode Project.md
@@ -1,3 +1,6 @@
-This Xcode project is for development only, it is not meant to compile production builds.
+This Xcode project is for development only, it is not meant to
+compile production builds.
 
-It is used internally to develop libzip and to run Xcode's diagnostic tools on the source.
+It is used internally to develop libzip and to run Xcode's diagnostic
+tools on the source, and is not always kept up-to-date. Please use
+the standard build method instead.