v1.7.0

Add support for rulesets in variables and passed to mixins to allow wrapping
Change luma to follow the w3c spec, luma is available as luminance. Contrast still uses luma so you may see differences if your threshold % is close to the existing calculated luma.
Upgraded clean css which means the --selectors-merge-mode is now renamed --compatibility
Add support for using variables with @Keyframes, @namespace, @charset
Support property merging with +_ when spaces are needed and keep + for comma separated
Imports now always import once consistently - a race condition meant previously certain configurations would lead to a different ordering of files
Fix support for .mixin(@Args...) when called with no args (e.g. .mixin();)
Do unit conversions with min and max functions. Don't pass through if not understood, throw an error
Allow % to be passed on its own to the unit function e.g. unit(10, %)
Fix a bug when comparing a unit value to a non-unit value if the unit-value was the multiple of another unit (e.g. cm, mm, deg etc.)
Fix mixins with media queries in import reference files not being put into the output (they now output, they used to incorrectly not)
Fix lint mode - now reports all errors
Fixed a small scope issue with & {} selector rulesets incorrectly making mixins visible - regression from 1.6.2
Browser - added log level "debug" at 3 to get less logging, The default has changed so unless you set the value to the default you won't see a difference
Browser - logLevel takes effect regardless of the environment (production/dev)
Browser - added postProcessor option, a function called to post-process the css before adding to the page
Browser - use the right request for file access in IE