Update imagemin to 2.0.0

When using the `use` option it throws an error. Working to fix that. Besides that it should be good.
Yeah optimizing it again is fine, I'm mostly concerned with file modified
date timestamp.

On Sat, Sep 13, 2014 at 2:11 PM, Kevin Mårtensson <notifications@github.com>
wrote:

> In tasks/imagemin.js:
>
> >
> > -                if (diffSize < 10) {
> > -                    msg = 'already optimized';
> > -                } else {
> > -                    msg = 'saved ' + prettyBytes(diffSize) + ' - ' + (diffSize / origSize * 100).toFixed() + '%';
> > -                }
> > +                    var origSize = stats.size;
> > +                    var diffSize = origSize - data[0].contents.length;
> > +
> > +                    totalSaved += diffSize;
> > +
> > +                    if (diffSize < 10) {
> > +                        msg = 'already optimized';
>
> I don't think there's a way to know if it's already optimized without
> optimizing it. Maybe comparing it with dest would work.
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/gruntjs/grunt-contrib-imagemin/pull/251/files#r17513870>
> .
>