(suggestion) make refresh_slow slow

[verga]

The difference between mkdp_refresh_slow = 0 or 1 is not so important; I suggest to change in autoload/mkdp.vim the 1 option

if g:mkdp_refresh_slow
    au BufWrite <buffer> call mkdp#markdownRefresh()

or something like this. It would need also (perhaps) a change in the initialization routine. In this way only writing the buffer would refresh the view: an option useful when the html is large and complex (many mathematical formulas, for instance). Thank you!!