Add link to vim-elixir in README
Add link to vim-elixir in README

beedub/elixir,ggcampinho/elixir,lexmag/elixir,michalmuskala/elixir,ggcampinho/elixir,gfvcastro/elixir,joshprice/elixir,gfvcastro/elixir,kimshrier/elixir,beedub/elixir,kelvinst/elixir,pedrosnk/elixir,pedrosnk/elixir,antipax/elixir,kelvinst/elixir,antipax/elixir,elixir-lang/elixir,kimshrier/elixir,lexmag/elixir