Merge pull request elixir-editors#397 from hauleth/feat/add-formatprg-value

Set formatprg to new Elixir format builtin

Author: jbodah

ftplugin/elixir.vim

@@ -30,6 +30,10 @@ let &l:path =
 setlocal includeexpr=elixir#util#get_filename(v:fname)
 setlocal suffixesadd=.ex,.exs,.eex,.erl,.yrl,.hrl
 
+if empty(&formatprg)
+ setlocal formatprg=mix\ format\ -
+endif
+
 let &l:define = 'def\(macro|guard|delegate\)p'
 
 silent! setlocal formatoptions-=t formatoptions+=croqlj