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/objacc.snippet

@@ -0,0 +1,11 @@
+- (${1:id})${2:thing}
+{
+	return $2;
+}
+
+- (void) set$2:($1)
+{
+	$1 old$2 = $2;
+	$2 = [aValue retain];
+	[old$2 release];
+}