feat: support less v4

[Helium-Z]

Hi Chris, I have removed the dependence on accord as your suggestion. And the new logic is totally extracted from the accord.
Please review the code and release a new version of this plugin

[yocontra]

Thanks @MisterLuffy - have you tested that this works across multiple less versions? I'm not sure what accord was doing to support all 3 versions, or if it was really this simple.

[Helium-Z]

Thanks @MisterLuffy - have you tested that this works across multiple less versions? I'm not sure what accord was doing to support all 3 versions, or if it was really this simple.

I have tested less v3 and v4, and the logic of extracting from accord is exactly same as before.
In fact, let accord support Less v4 is very simple, just need to change the name of this file to [2.x - 4.x.coffee]. Because accord only unifies the API parameters, and the render API between Less v3 and v4 has not changed.

[stamminator]

This PR resolves the failing Travis CI build case

[yocontra]

@MisterLuffy If you haven't tested it on the 2.x stuff it might be best to just drop support for that at this point - the next release (with these changes) is going to be a major bump anyways. 2.x is ~5yrs old and based on the npm stats not in wide enough usage to justify keeping support for it, most people are using 3.x and 4.x.

[Helium-Z]

@contra Agree with you. I have modified package.json and README, tested less v3/v4 and everything is fine

[ayyash]

Any updates to this, I can't wait :)