[FEATURE] Generate appcast.xml and release notes

- Generate the file using index.php which now exposes
  a simple API by passing a URI to the script.
Don't swallow sys.exit calls.
Reformat status message.
Don't swallow sys.exit calls
Write error messages to stderr.
[FEATURE] Create Sparkle appcasts for any app

- Exposes a simple command line interface to create Sparkle
  appcast.xml files.
- Includes extended RSS information to be used with RSS readers.
- Called with the --from-config flag, it reads the info necessary
  to create the appcast from the tools Makefile.config file.
- Create a new appcast, append new items to an existing appcast
  or replace any previous entries of an existing appcast with
  the current release.
Of course the branch is not supposed to be behind. Doooh\!