Enable nvim-tree to open dir during startup

Now when you open a directory when starting nvim, nvim-tree will be
opened to handle the directory correctly, see also issue #257.

lua/config/nvim-tree.lua

@@ -4,8 +4,8 @@ local nvim_tree = require("nvim-tree")
 nvim_tree.setup {
   auto_reload_on_write = true,
   disable_netrw = false,
-  hijack_cursor = false,
   hijack_netrw = true,
+  hijack_cursor = false,
   hijack_unnamed_buffer_when_opening = false,
   open_on_tab = false,
   sort_by = "name",