Sparkle updater added.
Sparkle updated.
Appcast URL updated.
launchd plist added.
[FIX] Updater now works for >= 10.6.
[FIX] Don't sign binary by default.
Add targets to build the sparkle updater.
[FEATURE] Update MacGPG2 via Sparkle.

- MacGPG2_Updater launches once a day and checks for new releases
  of MacGPG2
Copy org.gpgtools.macgpg2.updater.plist direct.
GPGTools_Core as a symlink.
Dependency should be MacGPG2_Updater not MacGPG2Updater.
Merge
Sparkle updated.
Sparkle appcast URL.
Make HOMEBREW_CACHE configurable for jenkins.
Merge branch 'sparkle-test' of https://github.com/GPGTools/MacGPG2 into sparkle-test
GPGTools_Core dependency removed.
Merge branch 'sparkle-test' of github.com:GPGTools/MacGPG2 into sparkle-test