A few changes to make checking unsaved changes a bit nicer:

- Write the file to a temp file using a shell command so <C-^> still
  brings up the previous buffer instead of the now-deleted temp file used
  for the maker.
- Add multiple log levels in g:neomake_verbose. This is nice because if
  you want to run :Neomake after leaving insert mode, you sometimes end
  up with too many messages. In this case you can do
      let g:neomake_verbose = 0