Update README for new release process.

README.md

@@ -1,4 +1,14 @@
-Introduction to Keychain
+IMPORTANT - GitHub Contributors
+===============================
+
+Please apply your patches to `keychain.sh`, *not* the generated `keychain`
+script, which we are now including in the git repo to facilitate the
+distribution of release archives direct from GitHub. The file `keychain` and
+related generated file (man pages, spec file) may be out-of-date during active
+development. We will regenerate them for official release archives only (those
+tagged with the release version.) Thanks!
+
+Please submit Introduction to Keychain
 ========================
 
 **Official documentation for Keychain can be found on [the official Keychain
@@ -15,3 +25,4 @@ time your local machine is rebooted. `Keychain` also makes it easy for remote
 cron jobs to securely "hook in" to a long running `ssh-agent` process,
 allowing your scripts to take advantage of key-based logins.
 
+