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/vim-snippets/UltiSnips/xml.snippets

@@ -0,0 +1,9 @@
+snippet t "Simple tag" b
+<${1:tag}>
+	${2:content}
+</${1/([\w:._-]+).*/$1/}>
+endsnippet
+
+snippet ti "Inline tag" b
+<${1:tag}>${2:content}</${1/([\w:._-]+).*/$1/}>
+endsnippet