Keep undo history

[powerman]

It would be cool if TOC modification done automatically done on save won't be added to undo history, so :w and u will undo last change user has done before saving, not TOC modification.

As example, https://github.com/fatih/vim-go plugin correctly does this while reformatting code on save by running external tools like gofmt or goimports.

[mzlogin]

Thanks for your advice. There is a issue #26 talking about this , maybe your suggestion would help.