vim: Make ftplugin tex.vim a symlink for plaintex.vim

For some reason I don't understand vim flip-flops between the two
formats, when there isn't really a reason to do that. This makes them
both the same, so I always get what I want.
Add new project to tmuxinator
vim: UltiSnips: Add new snippeets for tex

This adds writing snippets to tex files, these are really useful for
working on writing.