Stop Unite from overriding `startinsert` autocommands with `stopinsert`

I have this autocmd for vimshell: `au BufEnter [vimshell]* startinsert! | normal! G$`.
Without this change Unite overrules the autocmd.
Merge pull request #500 from joelmo/master

Stop Unite from overriding `startinsert` autocommands with `stopinsert`