Support for less@3.x

[josefguenther]

Looks like the (breaking) changes in less v3 aren't supported.

Assetic\Filter\LessFilter.php @ line 112: less.writeError(error);

less.writeError() is no longer a function, and throws an error. Would be nice to work with the latest version of less, ie 3.10.3.

[LukeTowers]

@josefguenther Try using the 2.0 branch of assetic-php/assetic. Until we tag 2.0, you can pull it in by using "assetic/framework": "dev-2.0/dev" in your composer.json files.

[LukeTowers]

@josefguenther We've just released the 2.0 release that addresses a number of existing issues and dependency updates, see https://github.com/assetic-php/assetic/releases/tag/v2.0.0 for more information! Please try it out and let us know if you have any issues!