Add nix support, closes #97

ftplugin/nix.vim

@@ -0,0 +1,17 @@
+if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, 'nix') == -1
+  
+if exists("b:did_ftplugin")
+    finish
+endif
+let b:did_ftplugin=1
+
+setlocal comments=
+setlocal commentstring=#\ %s
+
+" Nixpkgs indent settings
+setlocal tabstop=2
+setlocal softtabstop=2
+setlocal shiftwidth=2
+setlocal expandtab
+
+endif