Bump autoprefixer version, add option to disable it or provide configuration options

[PandaWhisperer]

Summary

Bumps the autoprefixer dependency to the current version 3.1.0.

Also introduces the ability to disable autoprefixer processing, if desired, by setting

"_autoprefixer": false

in a _data.json file when using harp. Alternatively, this key can be used to provide configuration options to autoprefixer, such as the browsers option, i.e.

"_autoprefixer": {
    "browsers": ["> 1%"]
}

This fixes #68.

Caveats

The _autoprefixer setting is only available on a per-directory basis, via _data.json, NOT in the global _harp.json.

[kennethormandy]

Thanks for the PR, but unfortunately we’re not going to be able to merge this for the reasons I mentioned here #68 (comment) Looks like you were writing this at the same time I was writing that, sorry.

We don’t plan to make Autoprefixer configurable, and Autoprefixer has already been bumped in the v0.9.2 release, which is here and will be merged soon.

We appreciate the PR, though. Let us know if there’s something else you’d like to tackle together.

[PandaWhisperer]

Yeah, I figured that, after reading your comment on the issue. Is there no way I can change your mind about this?

FWIW, I don't think doing it on a per-directory basis in a _data.json is ideal though. Can't think of many use cases where that would be necessary. But being able to set it project-wide in harp.json may be of use for some people.

[kennethormandy]

Yeah, sorry, I feel bad you had to go through the trouble of putting this together. Unlucky timing on our comments.

I agree that configuring the browser prefixes is a desirable feature of Autoprefixer, but for Harp removing having to “know” about this configuration is an even better feature. I think we’d be open to changing the defaults set within Harp if you have suggestions about that, but I would prefer not to expose them.