[NTG-context] Updated vim module

Hi all, I have released a new version of t-vim that relies on the t-filter module. The 2context.vim script that generates a ConTeXt file has changed. The generated file is now much cleaner (and read under a simplified catcodes). You should be able to update to a new version using ConTeXt minimals. This version supports - a syntax highlighting environment - an inline syntax highlighting macro - a macro to syntax highlight external files. See https://github.com/adityam/filter/blob/vim/doc/context/third/vim/vim.txt for brief documentation. The new syntax is not completely backwards compatible! Hopefully, this version will work correctly on all operating systems (No more quotes mess like the previous versions). Aditya