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/objc.snippet

@@ -0,0 +1,14 @@
+@interface ${1:`Filename('', 'object')`} : ${2:NSObject}
+{
+}
+@end
+
+@implementation $1
+- (id) init
+{
+	if (self = [super init])
+	{${3}
+	}
+	return self
+}
+@end