Support SCSS map

Input:

$breakpoints:(small: 767px,medium: 992px,large: 1200px);

Expanded output:

$breakpoints: (
  small: 767px,
  medium: 992px,
  large: 1200px
);

Nesting:

$map: (
    key1: value1,
    key2: (
        key-1: value-1,
        key-2: value-2,
    ),
    key3: value3
);

@include:

@include map(
  $dribble: #ea4c89,
  $facebook: #3b5998,
  $github: #171515,
  $google: #db4437,
  $twitter: #55acee
);