Updated all plugins that are non-forked. Added some new plugins.

Added update_plugins.py which can fetch new plugins from GitHub.

New plugins added: zencoding, vim-indent-object, taglist, nginx.vim

sources_non_forked/snipmate-snippets/objc/I.snippet

@@ -0,0 +1,6 @@
++ (void) initialize
+{
+	[[NSUserDefaults standardUserDefaults] registerDefaults:[NSDictionary dictionaryWIthObjectsAndKeys:
+		${1}@"value", @"key",
+		nil]];
+}