Create expected_output.css

Decorating url() breaks if passing more than one argument #674

It seems like the problem is isolated to the case where you pass more than 
one argument to @function url($arg1, $arg2: '') { ... }

My tests shows that:

attr() works with multiple arguments
omitting the second argument works
local function variables and global works
Note! When passing the second argument the last character of the first argument is removed