Cover type-of("red") case

This is a string, not a color.

Related:
    sass/libsass#1522
    sass/libsass#1525
    sass/node-sass#1175

Author: saper

spec/types/expected.compact.css

@@ -1,5 +1,6 @@
 div {
   color: color;
+  color: string;
   color: color;
   color: number;
   color: number;

spec/types/expected.compressed.css

@@ -1,5 +1,6 @@
 div {
   color: color;
+  color: string;
   color: color;
   color: number;
   color: number;

spec/types/expected.expanded.css

@@ -5,6 +5,7 @@
 
 div {
   color: type-of(red);
+  color: type-of("red");
   color: type-of(#abc);
   color: type-of(123);
   color: type-of(45px);
@@ -29,4 +30,4 @@ div {
   //foo + bar: 3px;
 }
 
-//@import url(type-of(3+3));
+//@import url(type-of(3+3));