* website
```
$map: (
test: 1,
black: 2,
);
@debug map-get($map, 'test');
@debug map-get($map, test);
@debug map-get($map, 'black');
@debug map-get($map, black);
```
The above code leads to a:
1
1
null
2
This is because maps' keys can be *anything* in sass (even other maps).
In the example, the map is defined with unquoted `test` and `black` as
keys which are understood as the string 'test' and the *color* black.
When asking for the value for the 'black' string key... there isn't any.
This commit forces the use of quoted string as color maps' keys.