Add rem fallback

[MoOx]

Not sure if this should be the default behavior.
We need make something like autoprefixer to select browser support.

[MoOx]

Ref #32

[bloodyowl]

why shouldn't it be the default behaviour?

[MoOx]

This is adding a lot of new rules. And it's only required for IE 8-.
And for one year I personnally only worked on IE9+ project.
But that why I created #32.

[bloodyowl]

it's not that much rules, is it?

btw IE8 is actually the lowest browser many people still have to care about (i.e. http://www.quirksmode.org/blog/archives/2014/09/ie_survey_resul.html)

[MoOx]

It can be a lot of if you use rem a lot. For my concern it's the unit I use the most now (maybe it's not a good thing). So it can easily create between x1.5 to x2 rules.
Anyway I can make it default & use false in my case, its not a big deal. The best option will be to rely on #32.

[bloodyowl]

yup
in most of my cases it's essentially for the grids and font-size reset after fixing the inline-block bug :)

[necolas]

Probably not worth the time

[MoOx]

I've take a quick look to add this feature (disabled by default) using node-pixrem (based on postcss), but the plugin is not exported & use a global option (ouch). This will need a PR to make things right.
I'm also seeing an interesting issue robwierzbowski/node-pixrem#5

[necolas]

It's only IE8 and Opera Mini without rem support. We don't even use fallbacks for new projects at Twitter :).

[MoOx]

I know, but I still have projects for client like Airbus that need IE8 support (mainly because they do not update their IT assets).
French are slow :)

[necolas]

Sure. But it can just be a postcss plugin right? Does it have to be included in this project?

[MoOx]

I think according to the way I load plugins (by using require() only when needed), it won't create any perf issue if it's defined as dep, but not required all the time.
And for now, we can't chain cssnext with others plugins (until postcss 3 is out).
Also, we are likely to be like autoprefixer in the future, & having deps that won't be used according to the browsers (so features) list. Don't you think ?

[MoOx]

Now that #32 has landed in master, I will add rem and it might be disabled by default according to browserslist default.