Added support for two arguments in hsla bif
Simplified rgba with one argument
Added `blend` built-in function
Added `luminosity` built-in function
Added `contrast` built-in function
Added setters for rgb components
Added setter for alpha color component
Added setters for hsl components
Refactored setters for rgba components
Simplified invert bif
Added `transparencify` built-in function
Merge branch 'feature-better-colors-transparentify' into feature-better-colors

* feature-better-colors-transparentify:
  Added `transparencify` built-in function
Fixed the algorithm for getting the alpha
Add `list-separator` bif. Closes #635
Add symlinks support to CLI. Closes #1195
Anonymous functions support. Closes #1575
illegal unary "%", missing left-hand operand. Fixes #1584
Another issue with cached imports. Fixes #1546
Allow idents and units coercion (consistent with strings)
Merge branch 'feature-coerce-ident' into rc-0.47

* feature-coerce-ident:
  Allow idents and units coercion (consistent with strings)